prime-select regression on kernel 4.15 and up

On Ubuntu 18.04, and as far as I can tell on any Linux distribution with kernel 4.15 or later, switching prime profiles now requires a reboot instead of logout\login which was required up to now.

Anyone knows if this is going to be resolved? Also, is there a possibility we’d get the same behaviour as in Windows, where not even a login\logout is required?

It has nothing to do with the kernel or the driver but Ubuntu changed the prime switch infrastructure completely. See this for info and a third-party fix:
To have it like in Windows, the nvidia driver would have to support render offload, which isn’t planned. You would have to use the nouveau driver for that. So no. See: