The script (attached to this bug) to install latest AMD drivers on ubuntu 19.04
for a RX590 on a Ryzen threadripper works for me, but leads to a Segmentation
fault at address 0x0 of /usr/lib/xorg/Xorg seen in .local/share/xorg/Xorg.0.log

Solution for me was to:
sudo mv /usr/share/X11/xorg.conf.d/10-amdgpu.conf
/usr/share/X11/xorg.conf.d/10-amdgpu.conf.bak
sudo mv /usr/share/X11/xorg.conf.d/00-amdgpu.conf
/usr/share/X11/xorg.conf.d/00-amdgpu.conf.bak
as proposed by axlc in https://community.amd.com/thread/227165
Then I had to reboot the PC, no more "loop login".