I also bought Plex years ago for 87€ but i gifted that account to a friend once i got jellyfin up and running.

You’re right - Jellfyin doesn’t have a native built-in way to access it from outside. That’s the reason Plex intercepts with their own servers when you do remote streaming, that’s one of the aspects you pay for.

Using tailscale (free and setup in like 5 min) you can access jellfin from everywhere. Easy peasy.

Rumor says that Plex also denies you remote access when you use a VPN or mesh like tailscale… so ymmv