@gpatel-fr it was about a year ago, I didn't do extensive testing, but none of the .mkv I tried worked, and .mp4 were very hit-and-miss. Good to know it isn't Hallium-related, perhaps there's hope to fix it on this device.
@Charly the issue w/ that is that, AFAIK, Libertine apps aren't hardware-accelerated, and video playback often gets choppy (it was one of the workarounds I tried). Didn't try the snap version though.