It’s difficult to say exactly what all a reverse proxy adds to the security conversation for a handful of reasons, so I won’t touch on that, but the realistic risk of exposing your jellyfin instance to the internet is about the same as handing your jellyfin api over to every stranger globally without giving them your user account or password and letting them do whatever they’d like for as long as they’d like. This means any undiscovered or unintentional vulnerability in the api implementation could easily allow for security bypass or full rce (remote code execution, real examples of this can be found by looking at the history of WordPress), but by siloing it behind a vpn you’re far far far more secure because the internet at large cannot access the apis even if there is a known vulnerability. I’m not saying exposing jellyfin to the raw web is so risky it shouldn’t be done, but don’t buy into the misconception that it’s even nearly as secure as running a vpn. They’re entirely different classes of security posture and it should be acknowledged that if you don’t have actual use for internet level access to jellyfin (external users, etc, etc) a vpn like tailscale or zero tier is 100% best practice.