Currently the Unifi Network Integration does not provide any entities for Ubiquiti’s Building Bridge devices such as the UBB or UBB-XG. Since these are always a pair of devices, if the link between them goes down, there is no way for HA to see this. The connected state stays up as one of the two devices remains online. This could be solved by passing the Link Speed, Link Quality, and Link Capacity values to entities in HA. All three of these values will drop out if the link goes down for any reason, allowing automations to kick off if HA could monitor them.