But our TeamSpeak server has 20 something channels, there are plugins written by community members that integrate with ARMA. And any other general group gaming that requires actual voice comms, it's Teamspeak or bust.
It was quite something to behold when I first joined the group, I had grown used to groups using one, the other, but not both. This group does it really well.
Though if you want to get old school, MPlayer did voice chat before it was "cool", way before 2005. If you remember what MPlayer is, you know you're already old.
Back then MPlayer was free, which is kind of where TeamSpeak/Ventrilo/Mumble fell off, either you had some technical know-how to host it yourself (and the bandwidth to do so properly) or you paid for hosted solutions. It was only a matter of time before a free solution came around and stole the user base with intelligent marketing, nice interface, and a decent product.
As someone who managed a gaming guild since 2005, I have seen many iterations. In the beginning it was all Skype, then we switched to Ventrilo and PhpBB, then many went to FB for text, then to Teamspeak for voice, then to Slack for text again, and now Discord for both text and voice.
The needs of the community didn't really change. They wanted persistent chat for text and images, put up announcements to guide new players, have votes/elections, and use team voice chats during play sessions. Each combination above solved those problems, each with its own unique benefits and drawbacks. Mumble's use case is exclusively on the team voice chats but it lacks any direct support for anything else which is likely why we never used it, even after I provided a server for free.
Nowadays I use my Mumble server for cooperative remote work, a job which it works perfectly for.