PPA for Ubuntu 20.04 does not work

[dnet890]

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Steps to reproduce the behavior:

1. type sudo sh -c "echo 'deb https://download.opensuse.org/repositories/home:/llamaret/xUbuntu_20.04/ /' > /etc/apt/sources.list.d/home:llamaret.list"
2. type wget -nv https://download.opensuse.org/repositories/home:/llamaret/xUbuntu_20.04/Release.key -O Release.key
3. type sudo apt-key add - < Release.key
4. type sudo apt-get update
5. type sudo apt-get install mystiq
6. I got error message:
   W: GPG error: https://download.opensuse.org/repositories/home:/llamaret/xUbuntu_20.04 InRelease: The following signatures were invalid: EXPKEYSIG B7BA3CECC420ED7D home:llamaret OBS Project home:llamaret@build.opensuse.org
   E: The repository 'https://download.opensuse.org/repositories/home:/llamaret/xUbuntu_20.04 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(8) manpage for repository creation and user configuration details.

Expected behavior
The PPA Should work

Screenshots

Desktop (please complete the following information):

• OS: Ubuntu 20.04
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.