Created attachment 135239 [details]
journalctl_amdgpu_4.14.0-041400rc7

I've had more luck with amdgpu. Well kinda. It finally boots without nomodeset
(starting from 4.13 kernel). But falls back to software rendering (Device:
llvmpipe). It also complains that:
amdgpu 0000:01:00.0: SI support provided by radeon.
amdgpu 0000:01:00.0: Use radeon.si_support=0 amdgpu.si_support=1 to override.

But when I start it with:
modprobe.blacklist=radeon radeon.si_support=0 amdgpu.si_support=1 

screen freezes, gnome doesn't start and it produces output from attachment.
Something about "dead whales":
lis 04 19:35:39 pc gnome-session-binary[1369]: CRITICAL: We failed, but the
fail whale is dead. Sorry....

There is also something about:
lis 04 19:34:09 pc org.gnome.Shell.desktop[1440]: amdgpu_device_initialize:
Cannot parse ASIC IDs, 0xffffffea./usr/share/libdrm/amdgpu.ids: No such file or
directory