Does the IKEA LILJEBAGGE work with HomeKit, Alexa, and Google Home?
The LILJEBAGGE radiator thermostat speaks Matter over Thread.
For phone control you need a Thread border router. It runs on batteries. It suits Home Assistant users, with native support through Matter over Thread.
How the device gets into the platform on this route. The headline is the best route: local before cloud, direct before bridged, core before community. The methodology page lists every level.