I assume it's very similar to what Home Assistant's backing commercial entity Nabu Casa sells with the "Home Assistant Voice PE" device, which is also esp32-bas

I assume it's very similar to what Home Assistant's backing commercial entity Nabu Casa sells with the "Home Assistant Voice PE" device, which is also esp32-based. The code is open and uses the esphome framework so it's fairly easy to recreate on custom HW you have laying around.