For a navidrome Android client, I use Symfonium, but it’s a paid Play Store exclusive. If you want FOSS, I’ve tried Tempus and it seems fine, the only reason I don’t use it is because I already paid for Symfonium

I use slskd (docker container for soulseek) to download music and Lidarr to automatically move it to an organized folder structure. Lidarr doesn’t natively connect to slskd, so you have to use an extension (which I forget the name of atm) to get them to work together. No part of this assumes that music has any metadata or that you want it, but Lidarr can be setup to automatically retag imported downloads with metadata from musicbrainz. I don’t do this, I prefer manually retagging with Picard

I don’t know what your experience with self hosting is, but I will say that I don’t think setting up a navidrome server is any more difficult than setting up a jellyfin server for shows and movies. Maintainability is pretty easy, just make sure that everything is updated every once in a while and you should be fine