nod I have had others tell me Threema is good, but it's a "walled garden" until now; Signal has won over hearts and minds by being FOSS and having no cost-based barrier to entry even for casual users. As a FOSS advocate I went with Whisper from the start and recommend Signal to everyone (with a fairly high take rate, non tech worker friends and neighbors) with a simple text link to install and saying something like "it's free and encrypted so nobody can see us talk." (KISS explanation)

(this is a US-centric comment, as phone numbers are rather static here; unlike other countries, not having a number isn't really how it works for most people on the big 4 carriers and their secondary MVNOs)