(In reply to Reimar Imhof from comment #18)
> That firmware kills kde / plasma5 and freezes the machine!
> 
> What I've done:
> Copied the firmware files to /lib/firmware/amdgpu/
> ran dracut to build new initrd
> reboot
> 
> graphical login comes up
> after logging in to kde plasma 5 the machine freezes
> 
> After a hard power of I logged into icewm.
> That desktop came up. I opened an console. Ok. 
> Started dolphin. Machine has frozen immediately. Even the clock in the
> desktop toolbar stopped working.
> 
> Before starting dolphin I had a look at dmesg. I couldn't find any new error
> messages. Unfortunately I do not have these messages around any more.
> I also had a look at the /var/log/Xorg.<i>.log
> There was no log written from the kde session freezing the machine.
> 
> Could you please test that firmware with a kde plasma 5 desktop? Please!

Can you just try updating the smc firmware?