I moved all our household content from Plex to Jellyfin a few months ago and it’s been pretty awesome. Can customize the shit out of it to suit your needs.
I have a QNAP server running it in a docker container and I’m not sure how to set it up on Apple TV. But if you do want external access without having to mess around with a firewall, tailscale works great and is fairly straight forward to set up.
Born and raised in Alberta, I’ve never heard of or seen this