Problems with certificates for custom multi-level subdomains


I’ve read the two other topics related to this but they both deal with default github-provided domain names wheres I have a custom domain. Should I be able to use multi-level subdomains in this case? Say something like

I’ve actually set this up for two (internal) repositories and it works fine with HTTP but neither has been able to generate a certificate. One has been stuck in 1/3 certificate creation for over 24hrs now with the message “Certificate Request Error: Certificate provisioning will retry automatically in a short period, please be patient.” while the other one just says “Something went wrong issuing a certificate for Please contact the Pages team.”

Edit: looks like the second one actually now works so this feature seems to be supported, which is great. However the other one is still stuck.

Turns out there is a limit on the length of the domain name. This is apparently not documented anywhere.