SOLVED: Jellyfin service not starting

[TheDreadPirate]

> Updating APT repositories.
Hit:1 http://gb.archive.ubuntu.com/ubuntu jammy InRelease
Get:2 http://gb.archive.ubuntu.com/ubuntu jammy-updates InRelease [119 kB]                                                                                               
Hit:3 https://brave-browser-apt-release.s3.brave.com stable InRelease                                                                                                                                 
Hit:4 http://gb.archive.ubuntu.com/ubuntu jammy-backports InRelease                                                                                                                                   
Get:5 http://gb.archive.ubuntu.com/ubuntu jammy-security InRelease [110 kB]                                   
Hit:6 https://downloads.1password.com/linux/debian/amd64 stable InRelease                                                 
Get:7 https://gerbera.jfrog.io/artifactory/debian jammy InRelease [4,080 B]                                               
Get:8 http://gb.archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages [1,277 kB]                       
Get:9 http://gb.archive.ubuntu.com/ubuntu jammy-updates/main Translation-en [261 kB]                     
Get:10 http://gb.archive.ubuntu.com/ubuntu jammy-updates/universe amd64 Packages [1,023 kB]                                         
Get:11 http://gb.archive.ubuntu.com/ubuntu jammy-updates/universe Translation-en [228 kB]                                         
Hit:12 https://pkg.cloudflareclient.com jammy InRelease                                                                               
Get:13 http://gb.archive.ubuntu.com/ubuntu jammy-security/universe amd64 Packages [826 kB]     
Err:7 https://gerbera.jfrog.io/artifactory/debian jammy InRelease                   
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY E7F84CDAE846576A
Hit:14 https://repo.jellyfin.org/ubuntu jammy InRelease
Reading package lists... Done
W: GPG error: https://gerbera.jfrog.io/artifactory/debian jammy InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY E7F84CDAE846576A
E: The repository 'https://gerbera.jfrog.io/artifactory/debian jammy InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure( manpage for repository creation and user configuration details.
Failed to update APT repositories. Something is wrong with your APT sources, GPG keys, or Internet connection. Try again shortly or use https://jellyfin.org/contact to find us for troubleshooting.

I don't think your server is actually pulling the jellyfin repo due to the issues you have with other repos.  Which is causing it to not pull down most of the packages.

In /etc/apt/sources.list.d/ remove the repo associated with  https://gerbera.jfrog.io/artifactory/debian.  Or comment it out temporarily.  Once you can get "sudo apt update" to run cleanly, redo the steps in my previous post.