I do not expect particular issues; for OL we’re also working to the pure OL7 to OL8 upgrade process.
BTW, I tested more times the moving from CentOS 7 to OL7 / oVirt to OLVM on 4.3 release.

I saw https://blogs.oracle.com/virtualization/getting-started-with-oracle-linux-virtualization-manager , but it's a little bit outdated and is about OLVM 4.2 + OEL 7 .

We’re now on OLVM 4.3.6+ (https://blogs.oracle.com/virtualization/announcing-oracle-linux-virtualization-manager-43) and working on latest maintenance release (on 4.3.10+).
The plan is to then work on OLVM 4.4 with OL8.

Simon,

How can I track the progress ? It seems that I need to migrate in 2 steps :
1) CentOS7/oVIrt 4.3.10 to OEL7 + OLVM 4.3.10
2) At a later stage to OEL8 + OLVM 4.4.+

I know that there is a centos to OEL script for the migration , but as oVirt (and most probably OLVM) requires some external repos - it will take some preparation.
Do you think that it's more reasonable to just reinstall one of the nodes to OEL 8 and then deploy the HE from backup (once 4.4 is available) ?
Then migrating the rest should be easier.

Best Regards,
Strahil Nikolov