Motivated users (which protesters definitely count as) will absolutely manage to successfully sideload an Android app. Especially seeing as how they are all routinely physically meeting up with many other protesters, so all it takes is running into someone who helps them get set up. Back in my Ingress days I had a similar situation where we were doing a big operation using a command and control coordination sideloaded app. Most of the people were able to figure it out ahead of time, but the last few had others help them download, install, and configure it when we met up for the op. Protests would be exactly the same thing.