android, add receiver block to the manifest, seems to be the last piece of the puzzle for getting a notification to go off, but was not a true alarm.

android/app/src/main/AndroidManifest.xml

@@ -37,6 +37,21 @@
         <meta-data
             android:name="flutterEmbedding"
             android:value="2" />
+
+        <receiver
+            android:name="com.dexterous.flutterlocalnotifications.ScheduledNotificationReceiver"
+            android:enabled="true" />
+        <receiver
+            android:name="com.dexterous.flutterlocalnotifications.ScheduledNotificationBootReceiver"
+            android:enabled="true"
+            android:exported="false">
+            <intent-filter>
+                <action android:name="android.intent.action.BOOT_COMPLETED" />
+                <action android:name="android.intent.action.MY_PACKAGE_REPLACED" />
+                <action android:name="android.intent.action.QUICKBOOT_POWERON" />
+                <action android:name="com.htc.intent.action.QUICKBOOT_POWERON" />
+            </intent-filter>
+        </receiver>
     </application>
     <!-- Required to query activities that can process text, see:
          https://developer.android.com/training/package-visibility and

lib/main.dart

@@ -173,7 +173,15 @@ class _HomeScreenState extends State<HomeScreen> {
   Timer? _alarmTimer;
 
   Future<void> _scheduleAlarm() async {
-    // Ensure that Android has the correct permissions enabled.
+    // Get the Notifications permission:
+    final android =
+        _notifications
+            .resolvePlatformSpecificImplementation<
+              AndroidFlutterLocalNotificationsPlugin
+            >();
+    await android?.requestNotificationsPermission();
+
+    // Ensure that Android has the correct alarm permissions.
     final canSchedule = await android?.canScheduleExactNotifications();
     if (canSchedule != true) {
       _showSnack('Permissions not yet granted, requesting...');
@@ -243,7 +251,12 @@ class _HomeScreenState extends State<HomeScreen> {
         uiLocalNotificationDateInterpretation:
             UILocalNotificationDateInterpretation.absoluteTime,
       );
-      _showSnack('Alarm scheduled.');
+      _showSnack('Alarm scheduled!');
+      debugPrint('DEBUG: Alarm time:   ${tzAlarm.toString()}');
+      debugPrint('DEBUG: Current time: ${DateTime.now().toUtc().toString()}');
+      debugPrint('DEBUG: ${_notifications.toString()}');
+
+      debugPrint('alarm: $tzAlarm, now: ${tz.TZDateTime.now(tz.local)}');
     } else {
       _showSnack('Platform not detected, unsure how to show alarm.');
     }