I gave a shot to implement first part of https://github.com/binwiederhier/ntfy/issues/6#issuecomment-1332280747.
For sure there are issues in this code, please don't be too hard with your review since this is my first time hacking on a kotlin project :-). I mostly did everything by copying existing code and by try and error. It isn't much battle tested either.
It allows to toggle a checkbox for each notification called "Own notification channels" in detail settings:
If toggled, it creates an own notification channel group with notification channels for each priority:
Notifications get sent to the correct group priority channel.
Default notifications (e.g. if the subscription does not use own notification channels) are grouped under a new "Default" group:
That's it.
This way you can set custom notification sounds, override dnd etc. per subscription.
Feel free to give your thoughts if this is something you want to have in your app or you think more of a different way to solve issue https://github.com/binwiederhier/ntfy/issues/6.