If you mean by “if I setup Zigbee2MQTT” a stand-alone Zigbee2MQTT instance, running on an Rpi or NAS or something, then yes, that publishes the zigbee devices in the same way as the Zigbee2MQTT app (addon) does in HA.
You’ll need to add a MQTT broker and MQTT integration to HA in order to be able to use these devices in HA & a Zigbee2MQTT instance (without HA, install MQTT Broker & Client apps on Homey)
(https://github.com/zigbee2mqtt/hassio-zigbee2mqtt).
Then, you’ll be able to add the Z2M devices to Homey per Homey HA Community app and/or by the Homey Zigbee2MQTT Community app.
The stand-alone Zigbee2MQTT instance need that MQTT system in place as well.
Then, you’ll be able to add the Z2M devices to Homey solely by the Homey Zigbee2MQTT Community app.
