The OERSI shared by @axel.klinger does not require (I believe) any end users to even touch GitLab/Github or even say the word “git” – If you look at the two examples he shared, they are both web sites at external links (technically one is published at GitHub but it is a stand alone web site).
If I understand right, an organization that has an OER Collection would import records to GitLab instance that could then be harvested/searched from OERSI. But all of the OERs exist elsewhere, it is very much a referatory. What he is showing is a functioning federated OER search.
This is covered in Axel’s 2022 presentation