I don’t know if this is normal now but since some update, when start my laptop a underscore have to pass over all the lines betwen the boot options and the lines of the bottom of the screen, I’ll attach a video, sorry for the out of focus but at least you can se the underscore moving on the screen.
The same for me, but after some kernel updates it disappears and later reappears. I’m not sure but I suspect it’s related to the graphics driver, but i am not able to find solution. Also in my case there is often situation when notebook stuck and not boot after grub.
It would be nice if you posted exactly what changes you made to the kernel command line so that others may be able to find a fix as well. Also it appears that a bug report with the fixes you found could help the maintainers in fixing the bug as well.
I can, but I believe it’s not important. I have problems with my notebook display, it’s detected as PSR2 panel and flickering. So in my setup, there is i915 param (i915.enable_psr=0) to disable PSR. Because there were some changes in PSR in the 5.13.4 kernel version, I tried to enable PSR and check if works or not. Was not working, so i revert it.
So obviously, if the change in the kernel command line affects the flickering, it does take place before the kernel fully loads. It is , after all, passed to the kernel by grub as parameters that affect the kernel and how the video driver is configured when loaded. The video driver gets loaded by the kernel.
It seems to me that it is directly related to the performance of the video on your system and directly affects the loading of the kernel.
Thank you for posting that so others may see it.
Also, Thank You for adding the reminder that:
After changing the kernel command line in /etc/default/grub, the final step involves running grub2-mkconfig before the change takes effect on the next boot.