Currently I use Jellyfin and found it simple enough to setup. My personal setup is https on the public internet using Caddy as a reverse proxy to handle the https part, but you can set it up for local network access only using http.
Jellyfin itself is not the greatest music player ever, (UI is more setup for movies and tv) but there are music-centric apps that use it as a backend that are really good, for most platforms. On my phone and tablet, I really like Finamp, and on the desktop I use Sonixd.
I’m also considering just getting a portable, 128GB FLAC player with a minijack connection and moving on with my life without getting involved in networking at all.
I used this setup for the better part of 20 years. Nothing wrong with it, my music collection simply expanded to the point where it simply wasn’t feasible to store all of it on my iPod anymore and from day to day I never really know what I’m going to be in the mood to listen to. Setting up a streaming service made more sense for me.