I've had multiple problems connecting Gitlab pages to my domain registered at Namecheap. I've tried multiple DNS configurations and none of them seem to work. I got "Failed to verify domain ownership" at the verification step, and even when I got past that (somehow), I got "something went wrong while obtaining the TLS certificate". I've followed the instructions given to me by GitLab (below), what am I doing wrong?
Answering my own question here, because I got in touch with Namecheap support. The example DNS entries provided by GitLab don't work on Namecheap (as of May 2022). The required DNS entries are
(Alias record) Host: www, Target: <gitlab_user_or_organisation_name>.gitlab.io.
(TXT Record) Host:_gitlab-pages-verification-code.www, Target:gitlab-pages-verification-code=<your_code>.
Note the differences to the Gitlab instructions. The Alias host is www, not www.<yourapp>.<tld>, and the verification host is _gitlab-pages-verification-code.www, not _gitlab-pages-verification-code.<yourdomain>.<tld>.
No CNAME record is required, in fact it conflicts with the ALIAS record anyway.