Unable to do obs game capture for vulkan window

obs gamecapture is not working for a vulkan window (war thunder on steam). the window (“aces”) appears in the dropdown in gamecapture but adding it shows a black screen.

i tried it out of the box, with game launch option obs-gamecapture %command% and then again with env OBS_VKCAPTURE=1 %command%. none of these made a difference. the necessary flatpaks (as per obs-vkcapture documentation) are already installed. i checked.

am i doing something wrong? any help is appreciated.