Ubuntu is fine, though with the recent rewrite of coreutils I’d be concerned about stability and bugs. That said switching distros is pretty easy, trying other distros in a VM is easy too. I always keep my data on another disk so it’s never affected if I break something. I recommend Mint (LMDE version) and Fedora Desktop with whatever desktop environment suits you.

I wonder which agencies and governments have access? I’m guessing bare minimum NSA, CIA, and higher level clearances at the FBI and DHS. Maybe even some of the 5 eyes countries. Definitely Mossad, that’s a given.