External 4k monitor doesn't power on with GeForce GTX 1660 Ti


I’m using an NVIDIA Geforce 1660 Ti board under Pop_OS! 20.10 and NVIDIA driver 460.56

Aside from the main laptop monitor, I plugged my NVIDIA card over HDMI to a 4k 3840x2160 LG monitor. It’s a dual monitor setup.

When I boot Linux and X starts (GDM), the LG monitor powers on very briefly showing a black screen, then it immediately powers off.

The LG monitor is set as the primary monitor. The laptop monitor, on the other hand, works without any problems, but I’m unable to see GDM’s login prompt because it is supposed to be displayed on the primary monitor, and it doesn’t turn on.

The only way I can make the LG monitor turn on is to temporarily switch to a random TTY with Ctrl+Alt+2, and then get back to GDM’s TTY with Ctrl+Alt+1. At that moment, the LG monitor works as expected.

Every time the monitor turns off (screensaver, suspend, etc) I have to do the same TTY hack to get it back working.

This problem doesn’t happen with NVIDIA driver 450. It happens only with 455 and 460.

This is my first post here, so let me know if I can reply with the output of some command or anything to make diagnosing the problem easier. Thanks in advance!