I have a bunch of belkin wemo, tp-link kasa and some other off brand smart switches that I use with home assistant locally. The problem I see here, is that as far as I know you still need the manufacturers app to link the smart switch to your network for the initial set up. The second they abandon the apps and stop updating them, people are gonna have problems. If you ever need to reset the switch, or change your WiFi SSID/password, or you move and have to set up the devices anew, you still need the manufacturers apps to do that initial set up.

I'm really hoping someone builds an app or service that can handle the initial handshake to get the device on your network from the initial WiFi hotspot they set up for their phone app to do its thing.