i agree with second half about SMS and email, but WhatsApp owned by Facebook is big no no and Viber isn't that popular, so i keep Signal and Skype Lite persona

i agree with second half about SMS and email, but WhatsApp owned by Facebook is big no no and Viber isn't that popular, so i keep Signal and Skype Lite personally i would not mind if we would use email as chat, there are already clients able to do that, it would solve lot of problems