Ubuntu/Debian Desktop Client install instructions do not work.

[mxa]

Following the installation guide for Ubuntu Debian on Kubuntu 24.04, I can't install Mattermost. The relevant terminal output here:

$ curl -fsS -o- https://deb.packages.mattermost.com/setup-repo.sh | sudo bash
Err:21 https://deb.packages.mattermost.com stable InRelease                                                                       
  The following signatures were invalid: EXPKEYSIG F8F2C31744774B28 Mattermost Build <dev-ops@mattermost.com>
$ sudo apt install mattermost-desktop
Package mattermost-desktop is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'mattermost-desktop' has no installation candidate

[mxa]

Solution is to remove the old offending key like this:
curl -fsS -o- https://deb.packages.mattermost.com/setup-repo.sh | sudo UPDATE_GPG_KEY=yes bash
via: https://forum.mattermost.com/t/mattermost-desktop-repository-install-on-24-04-lts-noble/18693/9