I just set up jellyfin last week. I am using a refurbished Dell optiplex 3050 micro running Ubuntu as server. I followed instructions on jellyfin documentation for installation. It was super easy, I was done in few hours.
I also used TecHuts Ultimate Jellyfin Media Server Guide for reference. Jellyfin have updated the installation process, so instructions on the video is slightly outdated. 1 command installs everything.