A lot of information is scattered about and it is difficult to find a solution that fits your situation. So you’ll have to filter a bit. There are loads of youtube tutorials out there and some of them are well supported by documentation, some are not. Be patient. My setup is basically a Jellyfin docker server with local storage so its easy for Jellyfin to see the files. Jellyfin is installed on Linux after installing docker. Jellyfin apps are installed on the devices I want to use to connect to Jellyfin. My router has Wireguard so I can connect to the router as a Wireguard VPN to listen to Jellyfin content. Thats it. My Jellyfin server is a 2 core i3-6006U laptop with a broken screen I had lying around. These days I think you’ll probarbly want to run an 8th - 9th gen Intel processor to support the latest features including GSync, but you don’t have to, try it on what you have. Once you have some hardware, look up how to install Linux, get a well known one like Ubuntu to begin with. Put some files in a directory , called say music for testing. Look up how to install Docker, then do that. Lookup how to install Jellyfin in docker. I’d use a .yml because you can change parameters easily and try again. Once you have jellyfin running go to the web interface and tell it where the music directory is so it can scann the files. All this occurs on your home network Install a Jellyfin app on your phone, connect to the server, play music locally. If you want to access away from home use some form of Wireguard VPN but you probarbly have enough to be getting on with. for now.

Edit: Forgot to say that if you struggle with docker, there is a direct install you can use. https://jellyfin.org/downloads/server Edit again: Documents here https://jellyfin.org/docs/