I enjoy working on selfhosted items and Jellyfin is in the mix. As with many software there are updates to them. Jellyfin seems to not have a great way to check for updates and install automatically. However, you can use the built-in API to help with that.
On Ubuntu the install.sh script adds a line to the sources list and that’s why an
apt update && apt upgradeworks./etc/apt/sources.list.d/jellyfin.sources