Welcome 
I am under impression that Matrix is using Jitsi Meet especially for group calls, but I don’t know are you trying to replace chat or 1:1 calls or them all, I haven’t tried calling in Wire or Signal, but Riot/Matrix is very heavy especially if you have a lower end phone like my Nokia 1. Also I don’t like Threema being closed source.
I also used to use Tox with my partner and the experience was horrible as it was missing support for multiple devices and often using a lot of battery and data. In the end we replaced it with XMPP server (edit3: this happened maybe two years ago, so I hope Tox has improved since then) ran by their friend and they are an admin. I guess my list would be:
- XMPP with technical users (or if you aren’t worrying about the server going down or burden of admining it)
- It’s said to leak some metadata (I don’t remember which exactly) to the server and your contacts, but you could connect to it over Tor and Tails ships with Pidgin (I hope in the future it will be Gajim), but Matrix/Synapse stores everything you do on the server forever so I guess that isn’t a problem for you (or you are unaware of it).
- Wire with not-technical users (my family) or users whom aren’t trusted with my phone number (it’s easy to say my username is
Mikaelaon Wire.com, I feel a bit paranoid with saying my phone number is+358...(for Signal)- However it also stores some metadata plaintext-accessible such as list of people you have contacted on Wire and possibly your groups (which Signal doesn’t even know about).
- Edit: I forgot to say that for some reason Wire rejected phone numbers of two of my family members on different days (and weeks) at first, so both originally registered by email and added phone numbers afterwards. I don’t know what caused that or if it was just temporarily, but it may be a too big step for some people and possibly a point for Signal
- Signal with whoever uses it and actively recommend it to current WhatsApp users.
- As I said, I don’t like phone number requirement
- I don’t like having a single master device either, even if linked devices keep working when your phone breaks) is a problem for me, I have had two family members cut out of WhatsApp group due to breaking mainboards or other technical problems (one of them was my grandmother who was calling or sending SMSes to some people about not having WhatsApp working, so please no single-device tied accounts for me, with Wire I could tell her to install it on her computer or login on the web app).
- But still, but it’s easy for anyone familiar with WhatsApp as it asks the same things (so people are probably easier to migrate on it), and they have actively worked to decrease metadata they see and everyone agrees it to be the most secure option, so I guess I have to support it (+ after I left WhatsApp, some of my contacts were there already
) .
Edit2: Wire requires Android 4.2+ while Signal requires Android 4.4+, I don’t know if this affects anyone, but some people in my circles price physical keyboards above everything else in a phone and thus have funny Android versions.
My answer seems to have gotten a bit messy, but I hope it will be of any help to you.
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