Truly awesome that this hobby is getting coverage! I'm very very lazy when it comes to self-hosting, by far my largest project was moving off Spotify and archiving all my playlists.
Rotating 3 API keys for spotdl and a YTP free trial for that sweet sweet 256kbps AAC then Musicbrainz Picard to label correctly all the music (automatic was nearly almost always wrong), then automating rebuilding the m3u8 playlists followed by the insane work of correcting all the little imperfections. Must've taken me like 2-3 weeks of just working on it most of the day.
But the result? A proper offline music library with all my main playlists with each song at the proper position and order in my playlists with the correct (Spotify) metadata using correct versions of the songs in at least 256kbps AAC (and many cases FLAC and where available non-vinyl hi-res).
Tossed on an old dell workstation I got for £50. Hosting navidrome where my JF, Qbittorrent-nox and Immich live. Using symfonium on my phone. Can access remotely via OpenVPN. Couldn't be happier.