I prefer Jellyfin over Plex. Plex has become too bloated. Jellyfin is free, open-source, and well maintained. I have it running on Docker on my NAS, feeding multiple devices, accessible on every platform I use, and it hasn’t failed me. I was a lifetime subscriber of Plex before I made the switch, and haven’t looked back.
LTT did a great video about Jellyfin. Keep in mind that this video is 5 months old, and they have had updates since.
Update: They weren’t able to renew the domain. They still own it, but they are using makemkv.info for the time being. Seems to be the forums only, for now.
https://forum.makemkv.info/forum/viewtopic.php?f=1&t=31225&sid=7e23b8e9c85e5d8a63df48c55b7dbb86
You can create accounts for Jellyfin that allows people to log in. However, the way you serve it to them is your responsibility. In my case, I set up my system with DDNS to work off a personal domain that anyone can connect to with the correct credentials. It’s a bit more work to set up, but I like it better in the long run.