Wow, that was a disaster. I installed the new AMD chipset drivers and got an MSFS slideshow, starting right from the menus. I enabled FPS counter and got 5 FPS in 4K. Task manager showed that CPU was about 5% loaded. Not the overall 5%, but the most loaded core was 5%. It won’t go past that. I rebooted etc. - nothing helped. As soon as I ununstalled the new chipset drivers and installed previous one - it all got back to normal just like that.
5900X, 3080, x570 chipset. So beware… Something is off here. Drivers are supposed to fix some CPU affinity related things, maybe that kills the FPS in some cases?