OVN between non-clustered hosts isn’t going to work well with Incus.
Incus expects to own the OVN deployment and be in control of all virtual switches, routers and ports. You can’t have one standalone Incus create a network and port and another Incus put instances on it.
Now for OVN on IncusOS, the way this works is that IncusOS runs both OVS and the OVN controller (ovn-host). The control plane (ovn-central) should be run in containers or VMs, possibly on the same cluster, just so long as they’re not themselves running on an OVN network.
For my test cluster, I have a single container running ovn-central which works fine, but for production environments we’re looking at stateless OCI images for the various OVN components so we could run those in HA mode across a cluster.