That mini-cannon seems difficult to aim, and wastes a lot of energy in recoil. It seems like it would be a great engineering experiment to figure out how to shoot that thing very precisely at distance.
As for the video, firing any sort of gunpowder indoors is asking for trouble.
If you do make the cannon, be sure to do read up and fully understand proof testing, then perform some proof testing, before playing with it. Think of it as a miniature hand grenade until you’ve reason to believe otherwise. You don’t want to be around it if things go wrong.
(FWIW, my father was a gunsmith and made pistols, rifles and cannons… I ain’t trolling here)