This sounds correct, what do you mean failed? Did you wait long enough (up to 48 hours)? The screenshot shows coverhack1 which doesn’t match the rest of your post.
In Glitch’s custom domain box, did you enter coverhack.novac.dev?
The A record is supposed to be for the main domain, I’d suggest removing it or using it for the netlify host.
As far as I know there’s no way to show it, likely its still pointing to the same project. For cleanup you can email glitch support to remove the unused one.
@novatorem do you possibly have on google domains, NS records pointing at netlify nameservers? If so, you’d need to add the subdomain CNAME to netlify’s DNS instead of Google’s DNS.
It does this for subdomain coverhack this is from an A record. Note that it doesn’t for cover-hack. It takes longer to remove the records from the various servers than it does to add them.
Looks like cover-hack is now working, in time coverhack should also.