Mumble can get very close if you tune it right.

To make it work well you Amy have to turn off lots of helpful processing that modern systems do.

Do you happen to know of any guides to doing this, or what specific settings/optimizations cause the most latency?

> The old analog POTS phone system wasn't like this.

I mostly agree with this, but POTS starting going digital surprisingly early, before VoIP ever became a thing. And of course digitization back then was typically chopping a huge amount of the high frequencies, making things sound...well, like the phone.

Yes, but it was using TDM near exclusively in the digital domain, and not packet switching like we do now, which lead to vastly different levels of service compared to now. The problem isn't digital, the problem is packet switching.

Most people making calls today have no conception of how good telephones used to be.

Sure. Packet switching allowed oversubscribing bandwidth, whereas previous digital telephony actually researched bandwidth (with TDM among other techniques).

Compressed cellular audio vs good landlines is a world of difference... and the modern cellular sound still sucks

The way to do it now is to make calls using an app via IP; FaceTime Audio is remarkably good even over 4G.

Sadly for some moronic reason FaceTime can’t use hardwired Ethernet. I have a reliable 4ms ping and Apple sells Ethernet adapters for iPads but FaceTime won’t use them.

Yeah systems like zoom are designed for enterprise where hundreds of simultaneous calls are happening on the same network. They work very hard to make those packets as tiny as possible.