One option I didn't see in the redhat doc was openvswitch. Don't they support it?
The link I posted was for RHEL 6. I just now saw that RHEL 8's documentation is online. I glanced through it and didn't see that mentioned. I'll read it more closely tomorrow.
There's no mention of openvswitch anywhere in that document. I am aware of XenServer and XCP-ng uses it by default. So its possible RHEL just prefers using macvlan/macvtap instead of openvswitch.