From their blog post about it:

An unauthorized third party accessed a limited subset of customer data from one of our databases. While we quickly contained the incident, information that was accessed included emails, usernames, securely hashed passwords and authentication data. Any account passwords that may have been accessed were securely hashed, in accordance with best practices, meaning they cannot be read by a third party.

The passwords were hashed and, I'm inferring from their language, salted per-user as well. Assuming a reasonable length password (complexity doesn't matter much here, what we want is entropy) it would take a conventional (i.e. not quantum) computer tens to hundreds of millions of years to crack one user's password.

… my personal Jellyfin server (nor anything else on it) has been hacked…

And I’ve never been attacked by a bear while wearing my goose feather headdress.