How do I set a base domain for gitlab's auto devops?
https://docs.gitlab.com/ee/topics/autodevops/quick_start_guide.html#install-ingress

Go back to the cluster page on GitLab, and go to the Details tab. Add
your Base domain. For this guide, use the domain .nip.io.
Click Save changes.

I think this option only showed up AFTER I installed the ingress.