

Matrix does have all of that, though? Except for voice.
I use matrix/element for socializing and Mumble for voice chat while gaming.
To respond to each comment:
- Element is a unified UI, available on PC/Web/Mobile.
- Starting and managing a community involves hitting the + button, creating a community, creating rooms in that community, then setting permissions and ACLs - pretty similar to discord, though with more control as you own the server.
- Embedded content is possible through the embed button.
- Video and voice work, but aren’t great for gaming (see below).
Element Call (aka the new MatrixRTC spec) is great for video calls, but leaves a lot to be desired for chatting while gaming.
QR code login is technically out, you just need to be running your own homeserver (and MAS) to use it.
But, yeah, exciting to finally have that.