Mumble is probably the best VOIP solution on the market. The main issue blocking its wider adoption, IMO, is the lack of support for persistent, multi-media friendly, text chat. I've suspected for a while that Discord could be totally replaced by someone duct-taping Mumble and some forum software together.
Same. I've thought about what Mumble needs to be competitive at all in the market.
* Persistent chat
* Multimedia chat (Emojis, resized images, etc)
* Camera streaming/game streaming (MUST HAVE these days)
Additionally, if there were "mumble multi-server management" that allowed a host to spin up other servers quickly, third-parties could skim off Discord. There is no loyalty to Discord IMO, it's just so damned easy to use.
Discord's biggest sell is being able to spin up your own "server" for zero effort and for free. Some kind of federated Mumble that people could rent servers from (or join their own self-hosted servers to) would be able to eat into some of Discord's market share but the free hosting is a huge draw ro Discord.