I have a working solution already so unraid isn’t really appealing to me, and as you say, isn’t FOSS. It’s one of the multiple reasons I’ll never switch to Plex, even if some argue it is a superior product to Jellyfin.
But I use NixOS (btw) so it’s fairly low maintenance once it’s setup, and easy to redeploy if things ever go completely sideways due to hardware failures etc
MP3 is fine if the bitrate is high enough and it was encoded with a semi-modern encoder. I still prefer FLAC so I can transcode it to whatever lossy codec I need without additional losses (usually Opus but there may be better codecs in the future).
Maybe Navidrome’s jukebox mode, although I suspect it’s a slightly different idea (and it was a bit buggy last time I tried it).
Many don’t run into dir structure issues because they have already organised their libraries with beets or an equivalent. I don’t personally have any issues with playing albums either. Some of the issues you are talking about seem to be client side, are you only testing the web interfaces?
Dsub2000 and Tempo are active FOSS alternatives.
I just overuse parantheses instead, as you noted. You know you’re rambling when you have several layers of them, like I’m writing a conversation in Lisp.
Having a web UI is useful even if you’re not using the extra tools. Not mandatory of course, but nice.
mpv supports Dolby vision (along with the Jellyfin clients that depend on it), but if you mean with streaming services, that’s unlikely to happen due to DRM.
If the jellyfin server is hosted on the same LAN as the Roku you should be able to access it without Tailscale at all using the IP address of the physical server and port number of Jellyfin. I.E don’t use the tailscale IP of the server when accessing from local devices.