L.A. Noire: The VR Case Files (722230)

( previously opened a dxvk issue here:
https://github.com/doitsujin/dxvk/issues/1538 )

When trying to play the VR game LA_Noire_The_VR_Case_Files (steamid 722230)
the game renders only in the desktop window, but stays black in the hmd (valve index). the headset and knuckles are recognized correctly (game window shows that moving your head controls the view, and knuckles do work), only the hmd stays black. maybe related to Rockstar Launcher overlay.
Software information

LA_Noire_The_VR_Case_Files
https://store.steampowered.com/app/722230/LA_Noire_The_VR_Case_Files/
default settings clean wineprefix, proton 5.0-5

GPU: GeForce RTX 2080
Driver: 440.64.0
Wine version: proton 5.0-5 -> wine-5.0-484-g26aac31
DXVK version: proton 5.0-5 -> DXVK: v1.5.5-21-g3d52ab36a

dxvk logs:
LANoireVR_d3d11.log
Launcher_d3d11.log

steam-722230.log (PROTON_LOG=1 %command% )
has an endless loop with
fixme:vrclient:ivrcompositor_submit_dxvk Unhandled flags 0x8.:

steam-722230.log

trying to get a apitrace the following log file (zipped) was produced with
"PROTON_LOG=1 PROTON_USE_WINED3D=1 %command%"
steam-722230.log.zip

Start by reproducing LA_Noire_The_VR_Case_Files with Proton 5.0-5 and the listed Valve Index setup, then review the attached dxvk_d3d11, Launcher_d3d11, and steam-722230 logs. Focus first on the repeated ivrcompositor_submit_dxvk message and compare behavior with PROTON_USE_WINED3D=1. Done means the game renders in the headset as well as the desktop window.