(which is silly because you can yell fire in a theater if, you know, the theater is on fire).
Actually I don't believe you can legally. The law was created in the belief the panic from hearing fire yelled would do more harm than good as panic stricken patrons trampled over each other to get out.
I'm not sure how you notify them without striking fear into them but I'm sure the law addresses that in the details
As far as OS you might want to give Linux Mint a try. They do a respectable job of polishing Ubuntu into a quite capable system.
whether I could persuade the drone pilots that they were.
Or weren't...A La Ender's Game. Make the drone pilot believe he is playing a training video game.