Yesterday I updated the our OLVM 4.4.10 Engine server (running Oracle Linux 8) - after a dnf update the OLVM UI wouldn't load - replaced with a '500 internal server error' message instead...
Luckily I knew how to fix this as Ovirt had the same issue about 6 months ago (and was fixed months ago in Ovirt)
If you have the same issue you need to downgrade the postgresql-jbdc package ,,,
# dnf downgrade postgresql-jdbc
Then restart Ovirt engine and it works again.
I do detect that this product isn't really well supported at least by the community, it seems insane there is no spice support at all in OLVM (at least 4.4) (see unanswered post from months ago -> https://community.oracle.com/tech/apps-infra/discussion/4502358/olvm-ol8-spice-support-completely-missing-how-to-enable) (note other people are having the same issue) as VNC is medieval in comparison. If you google 'OLVM spice' my post is the first one, which may tell you something about how well this product is supported.