Messages app/Gadgetbridge notifications broken by AntennaPod download/playback?

Yeah, that's actually what I suggested to the AntennaPod devs on GitHub - specifying "setLocalOnly(true)" on the download and service notifications.

The counterpoint I was given is that folks may want to see download progress on other devices. And with setAlertOnlyOnce(true) as documented on the page you linked to, presumably Gadgetbridge and/or Bangle.js should not be repeatedly showing the notification, only updating it.

From what I can tell, AntennaPod does reuse the notification ID to update the notification (rather than deleting and recreating)…

There is updateNotifications(), which is called by NotificationUpdater which specifies a fixed notification ID:

    private class NotificationUpdater implements Runnable {
        public void run() {
            Notification n = notificationManager.updateNotifications(downloads);
            if (n != null) {
                NotificationManager nm = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
                nm.notify(R.id.notification_downloading, n);
            }
        }
    }

(This notification ID and others are defined in the resources.)

Based on code elsewhere in the same file, this notification is updated once a second:

    /**
     * Schedules the notification updater task if it hasn't been scheduled yet.
     */
    private void setupNotificationUpdaterIfNecessary() {
        if (notificationUpdater == null) {
            Log.d(TAG, "Setting up notification updater");
            notificationUpdater = new NotificationUpdater();
            notificationUpdaterFuture = notificationUpdateExecutor
                    .scheduleAtFixedRate(notificationUpdater, 1, 1, TimeUnit.SECONDS);
        }
    }