Really good article. Thanks!
I would like to add that Signal currently works on only Androids and iphones, but Keybase works on both computers and phones, which is a significant advantage in my opinion. Of course both are constantly improving, so things will change.

Could you do an article on Keybase? I think there is more to it, as the core is not messaging, but PGP - and that made simple. Messaging is just one application that can benefit from PGP, but there is more too, isn't there?