If your music fits on your phone, you could just use Syncthing on your NAS and phone to simplify the process of adding new music to your phone.

I promise, you can say shit, ass and fuck

Why are you censoring your own text? Truly baffling.

I just subscribe with RSS to the releases page on github of each project

You can buy one exactly like this here: https://player-mods.com/

https://player-mods.com/ well you’re in luck cause you can buy them