To my knowledge a device can only be paired once to a homekit controller. I had my G2H paired to my iPhone as that was almost instantly as soon as you initiate the camera for the first time in the Aqare app. As soon as you unpair the camera in Apple Home, you can search for HomeKit enabled devices in Home Assistant using the HomeKit Controller integration. It will find the G2H after entering the HomeKit code manually.
Only issue I am now facing is that it only adds the motion sensor entity as part of the HomeKit Controller, not the camera itself as an entity.
It seems they are working on the HomeKit camera support currently: