The repository 'https://ppa.launchpadcontent.net/xrdesktop/xrdesktop/ubuntu jammy Release' does not have a Release file.
sudo add-apt-repository ppa:xrdesktop/xrdesktop
PPA publishes dbgsym, you may need to include 'main/debug' component
Repository: 'deb https://ppa.launchpadcontent.net/xrdesktop/xrdesktop/ubuntu/ jammy main'
More info: https://launchpad.net/~xrdesktop/+archive/ubuntu/xrdesktop
Adding repository.
Press [ENTER] to continue or Ctrl-c to cancel.
Found existing deb entry in /etc/apt/sources.list.d/xrdesktop-ubuntu-xrdesktop-jammy.list
Adding deb entry to /etc/apt/sources.list.d/xrdesktop-ubuntu-xrdesktop-jammy.list
Found existing deb-src entry in /etc/apt/sources.list.d/xrdesktop-ubuntu-xrdesktop-jammy.list
Adding disabled deb-src entry to /etc/apt/sources.list.d/xrdesktop-ubuntu-xrdesktop-jammy.list
Adding key to /etc/apt/trusted.gpg.d/xrdesktop-ubuntu-xrdesktop.gpg with fingerprint 1CCF10CCCA29CA9D1F14E480219F1335A1A17F3F
Hit:1 http://apt.pop-os.org/proprietary jammy InRelease
Hit:2 http://apt.pop-os.org/release jammy InRelease
Hit:3 http://apt.pop-os.org/ubuntu jammy InRelease
Ign:4 https://ppa.launchpadcontent.net/xrdesktop/xrdesktop/ubuntu jammy InRelease
Hit:5 http://apt.pop-os.org/ubuntu jammy-security InRelease
Hit:6 http://apt.pop-os.org/ubuntu jammy-updates InRelease
Hit:7 http://apt.pop-os.org/ubuntu jammy-backports InRelease
Err:8 https://ppa.launchpadcontent.net/xrdesktop/xrdesktop/ubuntu jammy Release
404 Not Found [IP: 185.125.190.52 443]
Reading package lists... Done
E: The repository 'https://ppa.launchpadcontent.net/xrdesktop/xrdesktop/ubuntu jammy Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.