This thread was a "why does remote access matter", not a comparison of Jellyfin and Plex.
I run both and Jellyfin is very clearly an open source project.
By that I mean that the interesting technical problem (streaming) is implemented rather well and there is a UI that technically has buttons to expose the things it does while simultaneously not being good at many of the things people use Plex for.
Jellyfin's remote access story is "set up a VPN or Tailscale". Plex's remote access story is "it works".
Jellyfin's story for accessing content from multiple servers doesn't exist. Neither does a global auth system for sharing access to your library, having friends, etc.
Jellyfin's sorting, filtering, and searching are just OK. Its web UI is nowhere near as nice for libraries of O(1000).
Real world example: I was at an AirBnB last week that had a Roku TV. To get to my Plex library I installed the Plex app. There was a Jellyfin app but I couldn't use it because there was no VPN client for the TV, and I don't feel the need to set up and run Tailscale when I already have Wireguard.
I use a reverse proxy for Jellyfin remote access, people saying you need a VPN or Tailscale (which is also a VPN) are unnecessarily paranoid IMO. That said, I'm a software engineer with more than 10 years of experience and a lifelong tinkerer, and I've set up an OpenWRT One as my primary router, so my firewall is more up to date and useful than 99% of consumers and I'm comfortable restoring a PC if it gets hacked.
But maybe more importantly IMO, Jellyfin doesn't have a central server that would serve as a high-priority target for hackers. Plex may have funding and full-time devs, but they're also relying on security through obscurity, which is hardly best-practice. Their central servers were hacked 10 months ago and passwords were leaked. For that to happen to me, hackers would have to be interested in my little Intel N100-powered server running from my house with maybe 10 daily active users. On top of that, Jellyfin's team have generally been quite fast at addressing all known high severity vulnerabilities because the project is open source. Everyone can see the code, so anyone can fix an exploit as soon as it's found.
As far as sharing access with my friends, I just ask them to put in the username/password they'd like on my phone in person for account creation, then I text them all the details about the URL for my Jellyfin instance, how to set up their smart TV app for it, etc.
I can access my Jellyfin instance from almost any smart TV in the world with the official apps because I followed their official guide and set up with a reverse proxy instead of Tailscale.
