I think the problem is that you haven’t actually deployed the OVN control plane.
Your DB string shows 3 IP addresses but then one of those at least is an IncusOS server. IncusOS ships the client bits of OVN (ovn-controller), it does not ship any of the control plane bits (ovn-central).
You need to setup ovn-central somewhere, either with just a standalone instance of it or a cluster of it (for HA), then you can have your IncusOS servers point to that ovn-central deployment.
In my own environments, I usually deploy ovn-central in HA with 3 containers running on the same Incus cluster that uses that ovn-central, just making sure not to use OVN for those containers as that’d obviously lead to failure 