Are you calling Service.StopAutomaticForeground? Try to create the notification with NB6.
Yes I have StopAutomaticForeground in Service_Start of FirebaseMessaging.
I do not create the notification.
I have just subscribed to a Firebase notification that is shown automatically when the App is in background.
The text, sound and icon is defined in the notification, comming fra an B4R project.
Works fine on older Android.
I have tried to remove the icon part from the notification, hoping it would use the default icon. No luck.
I found somewhere that I should create a ic_notification.png and put it in the mipmap folder, but again, no luck.
The icon used to be a white square until I change to an adaptive icon, now it is white round.