I'm not sure what I am missing, but isn't it completely possible to connect any kind of smart button to control a light bulb? Isn't this exactly what home assistant is being used for? I only tried it, but was able to add a generic smart button to HA and let it control a USB switch with some led lights. How is your use case different?

UPDATE: Ok, is this about the state of Matter implementation? I think I misunderstood that.