10/24/2018 (Wed) 01:07:30
Just to clarify, is your problem with matrix the lack of conference calls/ multi-way voip?
Matrix currently doesn't have it, but there is an experimental feature for it if you use riot as a client. There are also plans to support it officially in the future, but I haven't been able to find a date.
If you want conference calls, I've heard that jitsi might work. If you want to bother configuring everything, then XMPP can probably do everything you listed. The only problem is that it'll be difficult for less technically inclined people to use.
It can definitely satisfies 1, 2, 4, 5, 8, 9, 10. It probably satisfies 6 and 7. Not sure about 3. The problem is that some clients and servers don't support every feature you've listed.