Cannot detect the second monitor: nvidia driver 550, Ubuntu 20.04

Hello, In my Nvidia Settings none of the displays are detected. The main problem is driver can’t detect a second monitor. Dual monitor works well at Window by dual booting.


xrandr: Failed to get size of gamma for output default

I manually installed nvidia-driver-550.run because of the error which stuck in the blackscreen while booting Ubuntu. So I blacklisted nouveau and added nomodeset option like below.



I have been thinking about purging nvidia driver but, I afraid It will cause the same booting problem that happened before.

Nvidia-bug-report
nvidia-bug-report.log.gz (388.5 KB)