There's third party music-only apps like Jellify and Finamp, but they don't have the casting features that the official Jellyfin app has.

Shits a mess

Navidrome - no casting
Koel - no casting
Plex - no UPNP casting
Lyrion - good casting, but no web player, and doesn't support internet-exposed instance
Jellyfin - close, but no way to make the app music-only (has my movies). Casting a little buggy sometimes

They really should make these licenses transparent to the customer. That way we at least know that our game will be crippled after 5 years when making a purchase decision.

LMFAOOOO

Running OBS as administrator in Windows helps with low framerates for some game captures for me. Worth a try