[Blink] Expired certificate for Ubuntu Focal Repository?

[Lars Noodén]

Hello,

I am noticing some difficulty in updating Blink on Linux Mint.  Linux
Mint follows the Ubuntu Focal repository, but there seems to be an
expired certificate:

$ sudo apt update
...
Err:8 https://ag-projects.com/ubuntu focal Release

  Certificate verification failed: The certificate is NOT trusted. The
certificate chain uses expired certificate.  Could not handshake: Error
in the certificate verification. [IP: 81.23.228.137 443]
...

$ lsb_release -rd
Description:    Linux Mint 20.1
Release:        20.1

Who should be notified or is there anything I should do on my end?

Thanks.

/Lars