Seems like you followed some random AI generated guide like this one:
https://www.ipv6.rs/tutorial/Elementary_OS_Latest/Jellyfin/
Whenever you're downloading a Linux (or any) package, always try to look for the official documentation, like here:
https://jellyfin.org/docs/general/installation/linux#debian--ubuntu-and-derivatives
Where it will tell you to install Jellyfin on a Debian/Ubuntu based system is simply:
curl https://repo.jellyfin.org/install-debuntu.sh | sudo bash
and it also tells you that if you don't have curl already installed, either install it first or instead run:
wget -O- https://repo.jellyfin.org/install-debuntu.sh | sudo bash
which is their official installer.
If you want to undo what you did before installing (assuming you followed the bad guide linked above), just remove the file it created here first:
/etc/apt/sources.list.d/jellyfin.list