Certain terrain flickers. Ground/earth on side of grass planes and mountains/rocks. Plants and other greenery seem to be unaffected.

Also uploaded video clips and more pictures showing the issue to Firefox send (limited to 24hours, will renew link when necessary):
https://send.firefox.com/download/603dd3311b/#ghj0LzAff2ffInpu6hmBpQ
The clips show the issue best

Software information

Witcher 3 Wild Hunt
Vsync: On
Resolution: 1920 x 1080
FPS limit: 60
Everything else set to Ultra with exception of:
Detail Level: High
Shadow Quality: medium

Ran the game through Proton 3.16-6 Beta. Had the issue with non beta.
GPU: RX 580 Nitro+ 4GB
INTEL-MESA: warning: Haswell Vulkan support is incomplete deviceName = Intel(R) Haswell Desktop deviceName = AMD RADV POLARIS10 (LLVM 8.0.0)

server glx vendor string: SGI server glx version string: 1.4 client glx vendor string: Mesa Project and SGI client glx version string: 1.4 OpenGL vendor string: X.Org OpenGL renderer string: Radeon RX 580 Series (POLARIS10, DRM 3.27.0, 4.19.11-041911-generic, LLVM 8.0.0) OpenGL core profile version string: 4.5 (Core Profile) Mesa 19.0.0-devel - padoka PPA OpenGL core profile shading language version string: 4.50 OpenGL version string: 4.5 (Compatibility Profile) Mesa 19.0.0-devel - padoka PPA OpenGL shading language version string: 4.50 OpenGL ES profile version string: OpenGL ES 3.2 Mesa 19.0.0-devel - padoka PPA OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20

Attempts at finding the cause of the issue:

• Installed kernel 4.19, was at 4.15 prior to installation. No effect
• Toggled graphic settings on and off (vsync, window mode, etc) to see if flicker stopped. Only changing Texture quality had a impact but the issue of things not rendering was still prevalent.