Videos that are encoded with H.264 or VP8 codecs (possibly others too), regardless of the container (MKV, MP4, WEBM, etc), will only play audio in VLC, at least in Ubuntu 20.04. Interestingly, GNOME Video application will play those files just fine.
I've tried restarting the computer and let VLC run alone without any other user programs running concurrently to avoid interference. I've installed and reinstalled
gstreamer1.0-libav and various other packages, clearing
gstreamer cache and nothing changed. I've tried forcing VLC video demuxing to
H264 video demuxer but I've got the following error
VLC could not decode the format "h264" (H264 - MPEG-4 AVC (part 10)) which led me just to dead ends in Google Search.
What else can I try? I haven't found any other source in the web that have solved a case similar to mine.