Theres an open source app in the /e/app store which gets 10 out of 10 for privacy and its an add on for whatsapp to send only text message; without it accessing your contacts, called open in whatsapp yes thats the name of the app. could be good for solution for those that are stuck with whatsapp.
I didnt know about Jami and their strange name changes; 2 previous incarnations prior, so thats intresting. There`s some folks on the forum that think /e/ is a terrible name maybe /e/ OS should keep their current name and not change it for fear of critism of the name change 
To me theres nothing wrong with the /e/ name, i like it.
Thxs!!, i hadn`t heard about Signal, that looks like it could be a very good alternative to whatsapp, signal seems to be open source too, plus i like the forewords by snowdon and some Cryptographers!! That article you posted about facebook is very disturbing. its sounds very nefarious!
Asked the current status of this work and when it might be deployed in the production version of WhatsApp, a company spokesperson declined to comment.
That article is really amusing as then it suggests that criminals and terrorists will opt to use signal. doesnt mention us privacy advocates that dont want to be datamined, profiled and harrassed by advertisements.
The only issue i`ve discovered with Signal is that when the /e/OS does an update you lose your conversations, data, pictures etc unless use a method to back those files up as addressed in this /e/forum discussion here
I am unsure if its because it used to be included into the /e/OS and since removed from future OS updates, or it will be ok if you install it yourself from the app store. would be good to hear from those users and if Jami users encountered issues.
I did find another similar app called Jitsi meet however that gets a privacy rating of 3 out of 10, its very disapointing as i have been using Jitsi desktop version for windows for years to make SIP/ viop calls and was a fan. The desktop version is open source and supported by the community however their android app is not!; they got bought by a company called 8x8 not long ago 
a 3 out of 10 mark compared to the other messaging apps! wow this one must be really invasive.Yikes!
After browsing on the /e/ app store for awhile ive concluded that a privacy rating of 6 out of 10 is a very high mark for a text/ voice messaging app!