Xrandr can't open displays when trying Nvidia Optimus setup

[djhyland]

I recently purchased a new laptop (an Acer Nitro 5), and it came with Nvidia Optimus graphics (a GeForce GTX 1050 Mobile paired with an Intel UHD Graphics 630 Mobile). While I've succeeded in setting it up using the nouveau driver, I'd like to get the graphics working with the closed-source nvidia-drivers driver. I've followed the procedure in the Gentoo wiki to set it up, but I haven't had any luck yet. I think I'm close, but I'm still getting a black screen.

In going through the logs, I think that I get X using the nvidia-drivers correctly: there's no errors in /var/log/Xorg.0.log, and in fact, it says that the drivers start correctly. While figuring out my xorg.conf, I gradually eliminated the errors in Xorg.0.log, so I think I have it set up correctly. What I have noticed, however, is that my xrandr commands don't seem to work. I'm using lightdm as my display manager, and I've put the arguments in as recommended. Since I'm still getting a black screen, though, I tried running things manually (by removing xdm from the default runlevel, then entering the requisite xrandr commands and starting X manually) and noticed that all of my xrandr commands return the status "Can't open display". For example:

[hhfeuer]

Everything looks alright, just the display_setup.sh isn't called. Check that you properly set up lightdm config.
https://wiki.archlinux.org/index.php/NVIDIA_Optimus#Display_Managers