should work, it just works better with a trials unicycle because the tire has more volume and is stiffer overall so it has more bounce.
what would be considered a good trials uni, in terms of tire? I have a 20x2.5
it definately works cause ive tried it on my learners uni but it would probbaly take longer to learn and get the feel of a prehop
Trials unis usually have a 19" rim, but 20" will work. Because of the larger tire the outside diameter is still around 20". The width you have seems about right.
Also, trials tires tend to be “bouncier” than standard tires.