I would totally love to have .avi files working in Watch2Gether, because I and a friend of mine were trying to watch a series online, which I had in dvds (that I lost when moving houses), and I saved them into a cloud as .avis, the problem is, I can’t use them in W2G, which is kinda sad 
I’ve looked far and wide for other synchtubes that had .avi support, but with no avail. Hopefully they’ll add those in the near future, especially as Custom videos
try to use gaze long distance movie night service. if you and your friend have the identical video files locally (at PC), you can easily sync it.