Hi Theo,
The thing you mentioned - ovirt-administrator groups is a special construct with a purpose of having bootstrapped ovirt admin user for the new oVirt installations. This explains why Keycloak users assigned to that group, can for example, create new VMs.
Keycloak server bundled into oVirt setup serves only authentication purpose as opposed to the authorization, therefore, it is not required to create Keycloak group 'ovirt-student' and match it with oVirt counterpart.
If I understood correctly - users defined in keycloak can actually login to oVirt Admin panel and/or to ovirt vm portal, right?
If that's the case - you're simply missing some (group?) permissions - these permissions are only managed from within oVirt admin panel.
One more thing worth mentioning. In order to have some users under group defined in oVirt (via admin panel) you have to manually assign them there. User & group association defined in Keycloak is not propagated to oVirt. Although, it could be a nice feature to have!
Perhaps this documentation will help a bit:
cheers!
Artur