The author of the article mentions Signal as well, but how do you handle communication from a laptop or desktop computer and/or with people who don't own an Android or IOS smartphone?
Signal does have a desktop application. I believe you can also register a Signal account using a phone number from a service like Twilio. I'm not 100% sure that will work with Signal desktop though.
Signal in a chrome app can pair to signal on android/IOS. But I don't believe you can use chrome only. The chrome app just waits for you to pair with a phone and can't send/receive messages until you do so.
https://whispersystems.org/blog/signal-desktop/