Fully-managed GitHub alternative on a custom domain?

I am looking for a fully managed GitHub alternative that I could use on my own domain, but without having to handle or maintain any server (full-saas).

I looked at GitLab and would gladly pay to support it, but even in the paid plans it does not seem possible to use a custom domain, the repositories are always on `gitlab.com/example` rather than `gitlab.example.com`.