Bought a new gfx card RX 6600 to replace RX560 which had driver issue with UHD display (with 32" display roughly 2cm on right hand side there’s vertical area where even and odd lines are reverted and flickering - at least it looks like that, rest of the screen is fine) that apparently never gets solved (reported the problem well over a year ago, gave more info when requested but no progress). Tricky to install physically due to huge size.
Booting started fine but when graphics mode was activated at the later stage of the boot screen went blank. No signal to display. Tried HDMI cable - no change, tried different FullHD monitor - no change. Googled for quite some time before stumbled into solution.
Running command “inxi -Ga” revealed that X loaded actually Radeon driver and unloaded amdgpu. Why? Beats me but that was the case.
Changed grup config as per instructions:
GRUB_CMDLINE_LINUX_DEFAULT to have also “radeon.si_support=0 admgpu.si_support=1”. There used to be “amdgpu.dc=0” as well but took it out. Now X used correct driver.
So, no question this time. Just a solution/tip if you encounter such problem. Didn’t find thread/post with this problem here either.