[chirp_users] Install issues

[w4rss at radioclub.org]

I'm having issues installing the repository for Chirp in Ubuntu. I  
just installed the newest version of Ubuntu and then tried to add the  
Chirp repository to it.

Here is the output from the terminal:

  More info: https://launchpad.net/~dansmith/+archive/ubuntu/chirp-snapshots
Press [ENTER] to continue or Ctrl-c to cancel adding it.

Hit:1 http://us.archive.ubuntu.com/ubuntu focal InRelease
Hit:2 http://us.archive.ubuntu.com/ubuntu focal-updates InRelease
Hit:3 http://security.ubuntu.com/ubuntu focal-security InRelease
Hit:4 http://us.archive.ubuntu.com/ubuntu focal-backports InRelease
Ign:5 http://ppa.launchpad.net/dansmith/chirp-snapshots/ubuntu focal InRelease
Err:6 http://ppa.launchpad.net/dansmith/chirp-snapshots/ubuntu focal Release
   404  Not Found [IP: 91.189.95.83 80]
Reading package lists... Done
E: The repository  
'http://ppa.launchpad.net/dansmith/chirp-snapshots/ubuntu focal  
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.

Any suggestions how to overcome this?  The manpage is not really very helpful.

Thanks
Dick
W4RSS