Yeah, I ran a Mumble server for my group of friends for years. Basically zero maintainance beyond ensuring the package was up to date. The client was fast but as you said, setting it up was less friendly than Discord. Same thing happened, everyone moved to Discord.

Is there a guide or at least a pointer to what the server binary is? I haven't been able to find a headless one on a cursory search.

It's called murmur (mentioned elsewhere in the thread)

Thank you, once I knew the name, it was pretty much just an apt-get to set up.

My friends and I used to use Mumble, but setting it up was a pain in the ass. I spent several hours trying and failing to set up a local server before giving up and switching to a service whose bottom-tier servers were free (but also required a fair bit of setup). You had to do some tweaking just to use the client, too.

When the service I was on started charging even for their bottom tier, switching to Discord was a no-brainer. It just works right out of the box, at least for most people.

We used it for talkback in a video capture project I was doing at a broadcaster (before they built that functionality in natively) worked a treat.

Same here. I used to use Mumble as a way to get a bunch of remote voices into live video. Now I just use WebRTC via vMix Call, where I can mix it straight into my audio panel. Which is a better experience from a production side, but does have marginally more latency to deal with.