@cketti thanks for having a look at this. Your latest comments on github ticket pushed me into right direction - it was the same issue and solution as for my other thread
For whatever reason my notification settings whent back to importance medium/no sound - but it should have been importance high/quiet.
As it was working with 5.80x before I joined Beta 5.911 it might be an side effect of this update. But maybe it was some manual changes as at the same time I tried to make LED notification work with that Beta.