Sadly,
I have tried all of these and they all fall very short.

* Avoiding the pitfalls of centralized server (SPOF)
would be a first requirement.

This would put Retroshare Top of the list
but they have no iPhone or Android port.
This dooms it from even competing.
Nice idea, stillborn.


* I have tried all the versions of TOX:
although it has bugs and whatnot it would be nice,
except it has not yet developed viable group chat.
I am still seeking a method to create a group-cloud
to host long conversations.
It should be very possible to share
(as a p2p 'living document') a group discussion
but I am not there yet. (They are considering this)
The new NGC concept sounds like the right direction,
but not implemented yet.
< A specific use-case for a ethics-charity organization>
I like TOX a lot but it still fails group functionality.
- The other problem with Tox is that ordinary users might not
be found posting their Tox ID to connect.


* Matrix sounds nice but the homeserver design is a SPOF
Plus the fact that it seems to have evolved into yet another
hyper-complicated slogan-salad rah-rah contest.
the deal-killer is:
"...email addresses or phone numbers should be used publicly to identify Matrix users..."

* Riot is a glossy Matrix client.

All that said,
for some conventional organized comms venue,
some kind of Matrix looks okay for joe six-pack dialogues
but it looks like you need a server
along with all the conventional rubbish that means.
Like bending your knee to CA authorities
and all the DNS drama. PITA gravel sandwiches...
And not to forget there will eventually be
some kind of fealty checks on whether ->you<- are permissible.


One nice (current) summary about this sort of thing:

https://docs.google.com/spreadsheets...FOU/edit#gid=0


I have used Citadel for a long time.
It is functional for chats and discussions,
but it is a very old-school solution.
Think 1980's old-school.
It is free and a server can be setup without a domain name
and all that associated rubbish.
Users need no client - they can use a web interface
or even ordinary XMPP / email clients.
{users can also run federated servers if they wish,
it is an interesting option citadel provided long before Matrix etc}
They have dropped that feature recently

cheers