@areguera : do you confirm that it would be the simple case ACL (https://sigs.centos.org/guide/gitlab/#access) ?
That would mean having sig-artwork group (and so members) being owner on the artwork namespace and so you can then create sub-projects yourself

@arrfab : yes, I confirm. The simple case fits the needs at this moment.

One doubt related to:

This means, everyone added to this group on accounts.centos.org will be granted owner access to each and every project placed under that SIG’s namespace. This also means, that anyone not in this group will have no access at all.

Would this mean that people not in the accounts.c.o group wouldn't be able to even fork the repos to their own namespaces, and contribute MRs that way?

no, as you can see, projects under https://gitlab.com/CentOS are public and visible, so an existing gitlab user can fork/create MR against original project.
What I meant was that automatically added users to the sig-artwork group would be owners (all rights)
It's also best to ensure that you don't grant rights to individuals users (gitlab accounts) as it's then difficult to track ACLs

https://gitlab.com/CentOS/artwork is now created and the sig-artwork ACO group linked through SSO. So can you visit https://id.centos.org/gitlab to force initial SSO transaction and so confirm that you then have access to create sub-projects there ?
We'll then be able to close this request/ticket

@arrfab , I was able to login, and create a new project (https://gitlab.com/CentOS/artwork/centos-brand) successfully! It worked perfectly! Thanks!

thanks for feedback. closing if that works for you :)