OVN-Kubernetes RouteAdvertisements feature does not support dual stack BGP sessions:

			// If MultiProtocol is enabled (default) then a BGP session carries
			// prefixes of both IPv4 and IPv6 families. Our problem is that with
			// an IPv4 session, FRR can incorrectly pick the masquerade IPv6
			// address (instead of the real address) as next hop for IPv6
			// prefixes and that won't work. Note that with a dedicated IPv6
			// session that can't happen since FRR will use the same address
			// that was used to stablish the session. Let's enforce the use of
			// DisableMP for now.
			if !neighbor.DisableMP {
				return nil, fmt.Errorf("%w: DisableMP==false not supported, seen on FRRConfiguration %s/%s neighbor %s",
					errConfig,
					source.Namespace,
					source.Name,
					neighbor.Address,
				)
			}

However it has been acknowledged by FRR-k8s project that defaulting to dualstack BGP sessions through DisableMP=false was mistake and DisableMP has been deprecated and replaced with dualStackAddressFamily that defaults to false and thus dualstack BGP sessions are disabled by default.

Through this bug we should:
For OCP 4.20+:

• Replace the check for DisableMP=false in favor of checking for dualStackAddressFamily=true
• Explicitly document the incompatibility of using RouteAdvertisements together with FRRConfiguration or BGPPeers that set dualStackAddressFamily=true
  For OCP 4.19:
• Explicitly document the incompatibility of using RouteAdvertisements together with FRRConfiguration or BGPPeers that set DisableMP=false or omit setting DisableMP , or what is equivalent, that do not set DisableMP=true