Mqtt auto discovery - missing suggested_area per entity

I have a Relay Board, which I’m integration into home assistant over mqtt.

I’m using home assistant mqtt auto discovery

As a device, it is located in Room 1, but its “relays” control multiple rooms, and they are already described with tags: “Relay 1” → “Room 1”, “Relay 2” → “Room 2” etc.

My first approach was, to configure “suggested_area” per relay(entity), and then each relay would point to Relay Board through “device”. But I was surprised to learn that only “device” support “suggested_area” and it’s not configurable per entity.

I’m just now reading about device registry, and I understand that I should in fact register every relay as individual device, and then configure the parent Relay Board with “via_device”.

Am I on the correct path? Then what type/class should a relay board itself be registered as via MQTT?