back to auto and Kubuntu 26 installed with Nvidia driver 595 no problem. And incredibly it even works with my second screen at work now too. I can only assume that Windows has some kind of workaround for some bios settings like this. But Linux systems take the GPU selector to heart and really obey it? I don't know. All I can tell you is, it works. If you have a similar issue give it a go before you go reinstalling anything!

Don't be a fool like me!

https://redd.it/1tglwzr
@r_linux