Comment 39 for bug 1765363

For anyone who is looking for a solution to their problem with newer Nvidia cards and the regression that you need to reboot to switch graphics:
https://github.com/matthieugras/Prime-Ubuntu-18.04

I solved the problem by using bbswitch instead of nouveau to switch off the graphics cards and communication to a socket of a simple Rust program which kills the Xserver, and unloads the nvidia kernel modules without having to reboot.