Hello @es20490446e, the ATi Radeon HD5870 does not support Vulkan, which is required for DXVK to work inside of Proton. You may have luck adding PROTON_USE_WINED3D=1 %command% to the games launch options in order to use Wine's DirectX to OpenGL render path, but this comes with a significant performance penalty and is not considered supported.
@kisan-valve https://github.com/ValveSoftware/Proton/issues/3738
PROTON_USE_WINED3D=1x1 2020-04PROTON_USE_WINED3D=1 %command%x1 2020-04
What works under Wine doesn't seem to work at all with Proton.
Tried with both steam-manjaro and steam-native, also deleting the steam folders. I also tried listing missing libs following the instructions in the Arch wiki, but no missing dependency was listed.
Here's the log and, just in case you want to see further detail, a screencast.
My system specs are: