https://bugs.freedesktop.org/show_bug.cgi?id=102646
--- Comment #69 from Bastian brotwurst85@googlemail.com --- Distro/Kernel: Ubuntu 18.04.2/5.0.2 GPU AMD: Readon RX570 - Mesa 19.0 Display: Iiyama G23530HSU 75hz Desktop: Gnome
video: https://www.youtube.com/watch?v=gNJ2kJ8hsHA
Have the same problem as the op. The problems started with the 4.20 Kernels. Had not this problem with 4.19 LTS Kernels. The flickering doesn't appear on wayland if I choose only 60hz. On xorg it is irrelevant how much hz I use, it flickers regardless.
sudo -i echo "manual" > /sys/class/drm/card0/device/power_dpm_force_performance_level echo "2" > /sys/class/drm/card0/device/pp_dpm_mclk
Fixes the flickering.