https://github.com/jellyfin/jellyfin/is ... -794142731
-Download manual jellyfin-web package:
https://repo.jellyfin.org/releases/serv ... -1_all.deb
-This package appears to be in the /usr/share/jellyfin/web directory
-I deleted the contents of that directory manually.
-I installed the downloaded web package with dpkg -i.
-The web interface works again!

EDIT: The interface works but I can't paly content.
EDIT 2: https://github.com/jellyfin/jellyfin/is ... -794191785
Also if you end up removing dir /usr/share/jellyfin/web, you also lose given config file. So either back it up, or pull new from the same debian package. I had to do it manually for some reason.