Comment 11 for bug 1928138

 I changed that line so that it says:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash drm.debug=0x1e log_buf_len=4M"

and follower the rest of the steps.

when typing:
sudo dmesg | grep "Refresh Rate"
on the terminal, nothing really happens.

I am not sure I am doing that last step well, since I checked the previous ones.