Jellyfin works quite nicely and is very painless to setup. You can even sync your watch history from Plex ↔ Jellyfin using jellyplex-watched that works quite nicely. You can run both Jellyfin and Plex on the same server at the same time, pointing at the same media locations without issue.
Give it a shot and see if it meets your needs. It’s not perfect by any stretch, but it’s free.
