@Gargron Thanks for posting.
My 2-bobs-worth.....Been using Signal for a few years now...and it's initial product didn't have the "bells and whistles" like WhatsApp, but it has improved significantly...but one thing has been consistent ( as far I know), the security is pretty cool...
Only biggest issue is the size of the app/files....unlike WhatsApp there's no "relatively easy way" to migrate all media or even the app/file to external SD card...but suspect that is also due its security ethos..