Switchbot (hardware) and home assistant (controlling server) might fit your needs. It still would require an app, but home assistant is self hosted and is a fantastic automation platform. It won’t be as smooth as an all in one setup, but I find the tinkering is half the fun.

I’ve installed so many hardware items that are either “appless” and are controlled by home assistant or home assistant is compatible and replaced the app. Absolutely worth it IMO. I have been able to make a full self hosted/controlled and offline functional smart house.