Lack of the ability to create a project is definitely a shortfall in Gerrit, then as you said it is more for the Enterprise use case than massive hosting :]

I guess I will replace the content of the repos with a README.md pointing to the gitlab repositories then mark them read-only.

Thank you for your help,

Trust me, you can nuke. Anyway I've added the migration notes in the READMEs. Feel free to just set read-only and mark as resolved.

BTW, exactly as said @hashar, ironically Wikimedia CH deserves an enterprise tool but Gerrit is not a generic enterprise tool, but it's the WMF enterprise tool, and Wikimedia CH is out of this trust bounding. Fortunately GitLab namespaces are somehow more modern and flexible.

FYI I've also a small question here, just for my curiosity:

https://wikitech.wikimedia.org/wiki/Talk:Gerrit/Administration

(I don't love this solution of putting a new README on Gerrit since this will cause at least 2 orphan commits on Phabricator, when the Diffusion team will sync these repos to the new origin - that does not have these migration notes. But hey, if it's the only way, that's OK.)