Few video formats are not supported or videos just won't play. Sometimes restart fixes stuck videos.
"DirectShow" needs to be disabled (Settings -> Developer)
For Wayland use launch option (DeoVR & SteamVR):
env QT_QPA_PLATFORM=xcb %command%
Installed LAVFilters
Some videos (notably network ones) fail with "Unsupported format". I tried the DeoVR demo videos and some mkv files from my DLNA Server
Make sure "Unity player" and "DirectShow" are both disabled (Settings -> Developer)
Crashed on any video playback
Application starts, but trying to start any video causes it to instantly crash
Requires VP9 libraries like from LAVFilters to play any video. Tried the graphical installer, which had a failure during registration of the codecs. Tried running the .bat files from the ZIP, which didn't report any failure, but the game failed to launch anymore after this. See more here: reddit.com/r/SteamPlay/comments/b62pai/