Had to fix this, I thought to myself.
Context is, I have Ubuntu installed on Laptop on a dedicated SSD, and allocated 512GB for the main partition, I have 2 external monitors, one connected to HDMI(displays normal), the other connected to DP on the laptop, but DP port does not display.
After investigation, figured it might be NVIDIA video card serving DP but driver corresponding to linux kernel version not properly installed,
'uname -rs' #displays 5.15,
Software and updates, failed to switch driver for kernel 5.15, then swith to xOrg. driver, propted blank X alert, then reboot,
2 external monitors both have display, then go to settings->display, turn off display NO.1 and NO.3 for now, since NO.2 is 29 inch big enough for current concentration.
Other commands or CLI tools tried: dkms( dkms status: dynamic kernel management), nvidia-smi,
Aosl, there are some Linux run-level commands: init/telinit (0-6, 3 to command line networking with multiple users, 5 back to graphic user interface), use telinit, telinit 3, telinit 5,