diff --git a/app/build.gradle b/app/build.gradle
index 311f198..3023a88 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -34,20 +34,16 @@ android {
         debug {
             minifyEnabled false
             debuggable true
-            applicationIdSuffix ".debug"
-            versionNameSuffix "-debug"
         }
     }
 
     flavorDimensions "store"
     productFlavors {
-        forPlay {
-            dimension "store"
-            buildConfigField 'String', 'STORE', '"play"'
+        play {
+            buildConfigField 'boolean', 'FIREBASE_AVAILABLE', 'true'
         }
-        forFDroid {
-            dimension "store"
-            buildConfigField 'String', 'STORE', '"fdroid"'
+        fdroid {
+            buildConfigField 'boolean', 'FIREBASE_AVAILABLE', 'false'
         }
     }
 
@@ -81,7 +77,7 @@ dependencies {
     implementation "com.squareup.okhttp3:okhttp:4.9.2"
 
     // Firebase, sigh ... (only Google Play)
-    forPlayImplementation 'com.google.firebase:firebase-messaging:22.0.0'
+    playImplementation 'com.google.firebase:firebase-messaging:22.0.0'
 
     // RecyclerView
     implementation "androidx.recyclerview:recyclerview:$rootProject.recyclerViewVersion"
diff --git a/app/src/fdroid/java/io/heckel/ntfy/firebase/FirebaseMessenger.kt b/app/src/fdroid/java/io/heckel/ntfy/firebase/FirebaseMessenger.kt
new file mode 100644
index 0000000..e121d2f
--- /dev/null
+++ b/app/src/fdroid/java/io/heckel/ntfy/firebase/FirebaseMessenger.kt
@@ -0,0 +1,11 @@
+package io.heckel.ntfy.firebase
+
+class FirebaseMessenger {
+    fun subscribe(topic: String) {
+        // Dummy to keep F-Droid flavor happy
+    }
+
+    fun unsubscribe(topic: String) {
+        // Dummy to keep F-Droid flavor happy
+    }
+}
diff --git a/app/src/fdroid/java/io/heckel/ntfy/firebase/FirebaseService.kt b/app/src/fdroid/java/io/heckel/ntfy/firebase/FirebaseService.kt
new file mode 100644
index 0000000..51030ce
--- /dev/null
+++ b/app/src/fdroid/java/io/heckel/ntfy/firebase/FirebaseService.kt
@@ -0,0 +1,5 @@
+package io.heckel.ntfy.firebase
+
+class FirebaseService {
+    // Dummy to keep F-Droid flavor happy
+}
diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index a3f257d..549fd3d 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -53,9 +53,9 @@
             </intent-filter>
         </receiver>
 
-        <!-- Firebase messaging -->
+        <!-- Firebase messaging (note that this is empty in the F-Droid flavor) -->
         <service
-                android:name=".msg.FirebaseService"
+                android:name=".firebase.FirebaseService"
                 android:exported="false">
             <intent-filter>
                 <action android:name="com.google.firebase.MESSAGING_EVENT"/>
diff --git a/app/src/main/java/io/heckel/ntfy/app/Application.kt b/app/src/main/java/io/heckel/ntfy/app/Application.kt
index 79f3201..12e29f8 100644
--- a/app/src/main/java/io/heckel/ntfy/app/Application.kt
+++ b/app/src/main/java/io/heckel/ntfy/app/Application.kt
@@ -2,10 +2,8 @@ package io.heckel.ntfy.app
 
 import android.app.Application
 import android.content.Context
-import com.google.firebase.messaging.FirebaseMessagingService
 import io.heckel.ntfy.data.Database
 import io.heckel.ntfy.data.Repository
-import io.heckel.ntfy.msg.ApiService
 
 class Application : Application() {
     private val database by lazy { Database.getInstance(this) }
diff --git a/app/src/main/java/io/heckel/ntfy/ui/AddFragment.kt b/app/src/main/java/io/heckel/ntfy/ui/AddFragment.kt
index 160704c..3c923e8 100644
--- a/app/src/main/java/io/heckel/ntfy/ui/AddFragment.kt
+++ b/app/src/main/java/io/heckel/ntfy/ui/AddFragment.kt
@@ -15,6 +15,7 @@ import com.google.android.material.textfield.TextInputEditText
 import io.heckel.ntfy.R
 import io.heckel.ntfy.data.Database
 import io.heckel.ntfy.data.Repository
+import io.heckel.ntfy.BuildConfig
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
 
@@ -60,13 +61,20 @@ class AddFragment : DialogFragment() {
         useAnotherServerCheckbox = view.findViewById(R.id.add_dialog_use_another_server_checkbox) as CheckBox
         useAnotherServerDescription = view.findViewById(R.id.add_dialog_use_another_server_description)
 
+        // Show/hide based on flavor
+        instantDeliveryBox.visibility = if (BuildConfig.FIREBASE_AVAILABLE) View.VISIBLE else View.GONE
+
         // Build dialog
         val alert = AlertDialog.Builder(activity)
             .setView(view)
             .setPositiveButton(R.string.add_dialog_button_subscribe) { _, _ ->
                 val topic = topicNameText.text.toString()
                 val baseUrl = getBaseUrl()
-                val instant = if (useAnotherServerCheckbox.isChecked) true else instantDeliveryCheckbox.isChecked
+                val instant = if (!BuildConfig.FIREBASE_AVAILABLE || useAnotherServerCheckbox.isChecked) {
+                    true
+                } else {
+                    instantDeliveryCheckbox.isChecked
+                }
                 subscribeListener.onSubscribe(topic, baseUrl, instant)
             }
             .setNegativeButton(R.string.add_dialog_button_cancel) { _, _ ->
@@ -107,7 +115,7 @@ class AddFragment : DialogFragment() {
                 } else {
                     useAnotherServerDescription.visibility = View.GONE
                     baseUrlText.visibility = View.GONE
-                    instantDeliveryBox.visibility = View.VISIBLE
+                    instantDeliveryBox.visibility = if (BuildConfig.FIREBASE_AVAILABLE) View.VISIBLE else View.GONE
                     if (instantDeliveryCheckbox.isChecked) instantDeliveryDescription.visibility = View.VISIBLE
                     else instantDeliveryDescription.visibility = View.GONE
                 }
@@ -149,6 +157,6 @@ class AddFragment : DialogFragment() {
     }
 
     companion object {
-        const val TAG = "NtfyAffFragment"
+        const val TAG = "NtfyAddFragment"
     }
 }
diff --git a/app/src/main/java/io/heckel/ntfy/ui/DetailActivity.kt b/app/src/main/java/io/heckel/ntfy/ui/DetailActivity.kt
index a6da265..6d0ecd4 100644
--- a/app/src/main/java/io/heckel/ntfy/ui/DetailActivity.kt
+++ b/app/src/main/java/io/heckel/ntfy/ui/DetailActivity.kt
@@ -20,6 +20,7 @@ import androidx.core.content.ContextCompat
 import androidx.lifecycle.lifecycleScope
 import androidx.recyclerview.widget.RecyclerView
 import androidx.swiperefreshlayout.widget.SwipeRefreshLayout
+import io.heckel.ntfy.BuildConfig
 import io.heckel.ntfy.R
 import io.heckel.ntfy.app.Application
 import io.heckel.ntfy.data.Notification
@@ -372,7 +373,8 @@ class DetailActivity : AppCompatActivity(), ActionMode.Callback, NotificationFra
             val enableInstantItem = menu.findItem(R.id.detail_menu_enable_instant)
             val disableInstantItem = menu.findItem(R.id.detail_menu_disable_instant)
             val instantInfoItem = menu.findItem(R.id.detail_menu_instant_info)
-            if (subscriptionBaseUrl == appBaseUrl) {
+            val allowToggleInstant = BuildConfig.FIREBASE_AVAILABLE && subscriptionBaseUrl == appBaseUrl
+            if (allowToggleInstant) {
                 enableInstantItem?.isVisible = !subscriptionInstant
                 disableInstantItem?.isVisible = subscriptionInstant
                 instantInfoItem?.isVisible = false
diff --git a/app/src/main/java/io/heckel/ntfy/ui/MainActivity.kt b/app/src/main/java/io/heckel/ntfy/ui/MainActivity.kt
index 36c97f9..5f3de63 100644
--- a/app/src/main/java/io/heckel/ntfy/ui/MainActivity.kt
+++ b/app/src/main/java/io/heckel/ntfy/ui/MainActivity.kt
@@ -19,7 +19,6 @@ import androidx.lifecycle.lifecycleScope
 import androidx.recyclerview.widget.RecyclerView
 import androidx.swiperefreshlayout.widget.SwipeRefreshLayout
 import androidx.work.*
-import com.google.firebase.messaging.FirebaseMessaging
 import io.heckel.ntfy.R
 import io.heckel.ntfy.app.Application
 import io.heckel.ntfy.data.Subscription
@@ -27,6 +26,7 @@ import io.heckel.ntfy.data.topicShortUrl
 import io.heckel.ntfy.msg.ApiService
 import io.heckel.ntfy.msg.NotificationService
 import io.heckel.ntfy.work.PollWorker
+import io.heckel.ntfy.firebase.FirebaseMessenger
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.isActive
@@ -41,6 +41,7 @@ class MainActivity : AppCompatActivity(), ActionMode.Callback, AddFragment.Subsc
     }
     private val repository by lazy { (application as Application).repository }
     private val api = ApiService()
+    private val messenger = FirebaseMessenger()
 
     // UI elements
     private lateinit var menu: Menu
@@ -267,15 +268,7 @@ class MainActivity : AppCompatActivity(), ActionMode.Callback, AddFragment.Subsc
         // Subscribe to Firebase topic if ntfy.sh (even if instant, just to be sure!)
         if (baseUrl == appBaseUrl) {
             Log.d(TAG, "Subscribing to Firebase")
-            FirebaseMessaging
-                .getInstance()
-                .subscribeToTopic(topic)
-                .addOnCompleteListener {
-                    Log.d(TAG, "Subscribing to topic complete: result=${it.result}, exception=${it.exception}, successful=${it.isSuccessful}")
-                }
-                .addOnFailureListener {
-                    Log.e(TAG, "Subscribing to topic failed: $it")
-                }
+            messenger.subscribe(topic)
         }
 
         // Fetch cached messages
@@ -366,7 +359,7 @@ class MainActivity : AppCompatActivity(), ActionMode.Callback, AddFragment.Subsc
             subscriptionBaseUrl?.let { baseUrl ->
                 if (baseUrl == appBaseUrl) {
                     Log.d(TAG, "Unsubscribing from Firebase")
-                    subscriptionTopic?.let { topic -> FirebaseMessaging.getInstance().unsubscribeFromTopic(topic) }
+                    subscriptionTopic?.let { topic -> messenger.unsubscribe(topic) }
                 }
                 // Subscriber service changes are triggered in the observe() call above
             }
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index a5549d2..072a1e6 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -86,7 +86,7 @@
     <string name="detail_copied_to_clipboard_message">Copied to clipboard</string>
     <string name="detail_instant_delivery_enabled">Instant delivery enabled</string>
     <string name="detail_instant_delivery_disabled">Instant delivery disabled</string>
-    <string name="detail_instant_info">Instant delivery cannot be disabled for subscriptions from other servers</string>
+    <string name="detail_instant_info">Instant delivery is enabled</string>
 
     <!-- Detail activity: Action bar -->
     <string name="detail_menu_notifications_enabled">Notifications enabled</string>
diff --git a/app/src/play/java/io/heckel/ntfy/firebase/FirebaseMessenger.kt b/app/src/play/java/io/heckel/ntfy/firebase/FirebaseMessenger.kt
new file mode 100644
index 0000000..18b92f6
--- /dev/null
+++ b/app/src/play/java/io/heckel/ntfy/firebase/FirebaseMessenger.kt
@@ -0,0 +1,28 @@
+package io.heckel.ntfy.firebase
+
+import android.util.Log
+import com.google.firebase.messaging.FirebaseMessaging
+
+class FirebaseMessenger {
+    fun subscribe(topic: String) {
+        FirebaseMessaging
+            .getInstance()
+            .subscribeToTopic(topic)
+            .addOnCompleteListener {
+                Log.d(TAG, "Subscribing to topic complete: result=${it.result}, exception=${it.exception}, successful=${it.isSuccessful}")
+            }
+            .addOnFailureListener {
+                Log.e(TAG, "Subscribing to topic failed: $it")
+            }
+    }
+
+    fun unsubscribe(topic: String) {
+        FirebaseMessaging
+            .getInstance()
+            .unsubscribeFromTopic(topic)
+    }
+
+    companion object {
+        private const val TAG = "NtfyFirebase"
+    }
+}
diff --git a/app/src/main/java/io/heckel/ntfy/msg/FirebaseService.kt b/app/src/play/java/io/heckel/ntfy/firebase/FirebaseService.kt
similarity index 97%
rename from app/src/main/java/io/heckel/ntfy/msg/FirebaseService.kt
rename to app/src/play/java/io/heckel/ntfy/firebase/FirebaseService.kt
index d61006f..5d8aff6 100644
--- a/app/src/main/java/io/heckel/ntfy/msg/FirebaseService.kt
+++ b/app/src/play/java/io/heckel/ntfy/firebase/FirebaseService.kt
@@ -1,4 +1,4 @@
-package io.heckel.ntfy.msg
+package io.heckel.ntfy.firebase
 
 import android.util.Log
 import com.google.firebase.messaging.FirebaseMessagingService
@@ -6,6 +6,7 @@ import com.google.firebase.messaging.RemoteMessage
 import io.heckel.ntfy.R
 import io.heckel.ntfy.app.Application
 import io.heckel.ntfy.data.Notification
+import io.heckel.ntfy.msg.NotificationService
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.launch