If you expose Jellyfin on 443, have HTTPS properly set up (which Caddy handles automatically), your admin password is not pswd1234 (or you straight up disable remote admin logins), and use a cheap .com domain rather than your IP--what is the actual attack surface in that case?

As far as I can remember that is more or less what is usually suggested by Jellyfin's devs, and I have yet to see something that convinces me about its inadequacy.

He claims there are known exploits. Though I also want to know if this is really true.

https://github.com/jellyfin/jellyfin/issues/5415

The absolute worst thing I can see in there is that an third party who somehow managed to get a link to one of your library items (either directly from you or from one of your users--or by spending the next decade bruteforcing it I guess) could stream said item: https://github.com/jellyfin/jellyfin/issues/5415#issuecommen...

Everything else looks to me like unimportant issues, that would provide someone who's already logged in as a user minor details about your server.