Environment:

VKD3D_CONFIG=force_host_cached,dxr
VKD3D_FEATURE_LEVEL=12_1
RADV_PERFTEST=rt

Relevant lines from the log file:

Proton: 1694824757 experimental-bleeding-edge-8.0-56010-20230915-pf87ff9-w4dafea-d83dc46-v88e4f3
Assertion failed: !succ->pred_back_edge || succ->pred_back_edge == &entry, file ../src-vkd3d-proton/subprojects/dxil-spirv/cfg_structurizer.cpp, line 2058

This happens quickly, when the Bethesda logo is being (or is about to be) displayed.