Wanted: electronically switchable crossover / changeover switch

Then you should use KNX directly and not a (complex) DIY solution.

I'm thinking about KNX; the pros and cons are always being discussed here. Do you know a KNX switching actuator that I can combine with a conventional two-way switch? Or would everything have to run via KNX then?

The light switch is always set to "ON".

Your approach can do a lot. But the thing with the switch that you usually aren’t supposed to use isn’t so nice. If you remove it, the desired independence from the smart home part is also gone.

I am thinking about KNX, advantages and disadvantages are always discussed here. Do you know a KNX switching actuator that I can combine with a conventional two-way switch? Or would everything then have to run via KNX?

Either KNX or conventional. A middle ground makes no sense – I also don’t drive a car with a petrol engine in the front and a diesel engine in the back.

What I still haven’t understood is whether you are thinking about a new building or an existing building.

What I still haven’t understood is whether you are thinking about a new build or an existing building.

New build. And I am in the early planning stage (at the moment we are still moving walls back and forth with the architect). I am still organizing everything that comes after the building application in my head.

Sounds a lot like an incomprehensible patchwork solution. Please either go smart or not. Given how big the fear of smart seems to be, I would recommend a classic installation. You are not independent through the cross-switch tinkering anyway. If you want the light off and the "smart" part keeps turning it on again, that doesn't help anyone.

Your approach can do a lot. But the switch, which normally should not be used, is not so nice. If you remove it, the desired independence from the SmartHome part is also gone.

There are already flush-mounted solutions from Hue. Then you only replace the switch in the wall box, you can leave the "underlay" as it is. The conversion should only take a few minutes.

A little "smart" is like a little pregnant, that doesn't work either. ;)