Answer by jeremy_rutman for External Monitor not working. Ubuntu, nvidia

I also don't get my external display recognized, after a month or so working normally with ubuntu 20.04xrandr gets me :

...   320x180       59.84    59.32  DP-1-1 disconnected (normal left inverted right x axis y axis)HDMI-1-1 disconnected (normal left inverted right x axis y axis)

I already have secureboot disabled.I tried commenting

# options nvidia-drm modeset=1

in /lib/modprobe.d/nvidia-kms.confand still nothing. Also did

sudo apt-get install linux-modules-nvidia-390-generic

and also tried prime-select intel and back again to nvidia, so far nothing has helped. When in nvidia mode I do get an ok response from nvidia-smi namely

jeremy@jeremy-Blade:~/$ nvidia-smiThu Dec 10 18:27:28 2020       +-----------------------------------------------------------------------------+| NVIDIA-SMI 455.38       Driver Version: 455.38       CUDA Version: 11.1     ||-------------------------------+----------------------+----------------------+| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC || Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. ||                               |                      |               MIG M. ||===============================+======================+======================||   0  GeForce GTX 1060    Off  | 00000000:01:00.0 Off |                  N/A || N/A   67C    P3    22W /  N/A |    285MiB /  6078MiB |     21%      Default ||                               |                      |                  N/A |+-------------------------------+----------------------+----------------------++-----------------------------------------------------------------------------+| Processes:                                                                  ||  GPU   GI   CI        PID   Type   Process name                  GPU Memory ||        ID   ID                                                   Usage      ||=============================================================================||    0   N/A  N/A      1186      G   /usr/lib/xorg/Xorg                 45MiB ||    0   N/A  N/A      1773      G   /usr/lib/xorg/Xorg                184MiB ||    0   N/A  N/A      1934      G   /usr/bin/gnome-shell               32MiB ||    0   N/A  N/A      3435      G   /usr/lib/firefox/firefox            1MiB |

What finally solved this for me was install of latest nvidia driver.