When of my biggest pet peeves is not that notification sounds play while listening to music, but that they briefly power its volume. Its like dancing in a club and you get a notification about your uber eats and so the dj tells everyone to quiet down for a bit so that you look at the message.

I am pretty high while writing this, so, just to be safe, here are similar issues:
https://android.stackexchange.com/questions/204153/disable-or-change-audio-ducking-lowering
which was deemed answered by https://android.stackexchange.com/questions/199918/stop

-notifications-from-briefly-lowering-media-volume.

Seems like your links answer the question: it's up to the app playing music, and there are some suggestions of apps that let you choose.

I was always the guy who made custom notification sounds for every app, going back to the flip phone days. Until I got a Pebble watch back in 2016 and permanently put everything on vibrate-only.

Last year, I went back to a regular watch and turned on the notification sounds again...

Anyway, I turned them all off a few days ago for some reason, and just haven't cared to turn any of them back on. It's been really nice. I think I'm going to just set a notification for phone calls, and texts from my wife.

I miss having a phone where vibrate was useful. I'd really prefer that over sounds.

My OG Droid would wake the dead.

😕

Use a music player that has a setting for it. I'm a poweramp fanboy

A useful vibration is one you can feel, not hear from across the room.

I do similar, but in my case I made all notifications silent minus three total apps: the app my wife and I use to text and the two different apps my kids teachers use.

It's... so nice. It's almost as rewarding as my recent email unsubscing binge and setting up rules some of the other stuff I want to keep out of the spotlight.