I installed 19.09 on an old lenovo t420s and new lenovo p52s. Only on the p52s model i am not able to restart or shutdown my computer. It freezes and is not coming back. The configuration on both computers is the same, this is why i am wondering.
After some more research i think nvidia is the problem. Journalctl shows that xsession at each shutdown hangs. Due to segfaults with the nvidia driver. I tried
services.xserver.videoDrivers = [ "intel" ]; in my configuration.nix which works.