GitLab product person here - Thanks for the suggestion! I think this issue (scheduled for our 12.6 release coming out next month) should help. https://gitlab.com/gitlab-org/gitlab/issues/27630
Yes, I was talking about deploying to our existing cluster. Pretty much the only requirement for software that we run is that it must run in our cluster.
Ironically, it's often harder to deploy applications that offer their own k8s deployment approaches because they often have their own opinionated ways of using it that don't match our policies.