Installation over Ubuntu/xubuntu 22.04.03 broken?

[Req]

I have an Ubuntu 22.04.03 system over which I did apt install xubuntu-desktop and logged into a xubuntu session.

I'm trying to follow https://software.opensuse.org//download.html?project=home%3Abgstack15%3AChicago95&package=chicago95-theme-all that instructs the following steps

echo 'deb http://download.opensuse.org/repositories/home:/bgstack15:/Chicago95/xUbuntu_22.04/ /' | sudo tee /etc/apt/sources.list.d/home:bgstack15:Chicago95.list
curl -fsSL https://download.opensuse.org/repositories/home:bgstack15:Chicago95/xUbuntu_22.04/Release.key | gpg --dearmor | sudo tee /etc/apt/trusted.gpg.d/home_bgstack15_Chicago95.gpg > /dev/null
sudo apt update
sudo apt install chicago95-theme-all

During apt update I get a GPG error;

W: GPG error: http://download.opensuse.org/repositories/home:/bgstack15:/Chicago95/xUbuntu_22.04 InRelease: The following signatures were invalid: EXPKEYSIG FB2572B7B977DBCD home:bgstack15 OBS Project home:bgstack15@build.opensuse.org
E: The repository 'http://download.opensuse.org/repositories/home:/bgstack15:/Chicago95/xUbuntu_22.04 InRelease' is not signed.

Is the gpg file incorrect? Should I do something extra?