Using DXVK 0.94, on Linux Mint 19 (Cinnamon) 64-bit. My only workaround is to just record it with OBS as its being played back in the game while running in Windowed mode. It doesn’t seem to get recorded when in Full Screen mode in OBS, since it’s just black screen, probably because it’s using Hardware Acceleration to draw in full-screen.
I know this is an older thread, but I ran into this problem with Overwatch 2 and this was the first page Google threw at me. Thought I’d share that the webm exporting doesn’t work anymore - it spits out a ~600kb file that cannot be read by video players. As far as I could find, there’s no fix for this problem, but there’s a workaround.
I copied the files in [prefix root]/drive_c/users/[username]/AppData/Local/Blizzard Entertainment/Overwatch to a Windows drive and I could export the highlight I wanted from running the game there. It is far from an ideal solution, but it works.