The repository ' stable/ Release' no longer has a Release file

What’s the appropriate action here? Wait for that to be fixed? Bypass the caution about it?

Well I actually don’t understand why you have this error. It works well for me, and the Release file is definitely there on Index of /stable.

Are you sure the server where you are using apt have access to Index of /stable, any other error or warning before this one ? Maybe some certificate problem related to recent root certificate change in Let’s Encrypt.

Yeah, now there’s an error earlier than that which either was not there before, or that I missed;

Err:7 stable/ Release
Certificate verification failed: The certificate is NOT trusted. The certificate chain uses expired certificate. Could not handshake: Error in the certificate verification. [IP: 443]

Yup. Needed to remove the xwiki apt source, upgrade the rest first – most certainly the ca-certificates package had the new Let’s Encrypt root. Guess there’s no way to get apt to be elegant about that sort of unusual dependency.

Yeah not an easy thing to resolve for APT.