[upofadown]

>That "carrier grade Discord type thing" is more or less standard SIP VoIP, just over a prioritized data channel...

It is completely restricted to one SIP provider. Which raises an interesting idea for improved competition. Make it possible for the user to choose their SIP provider. Force the phone companies to allow the use of that priority to any SIP RTP stream and otherwise make those companies just sell data service.

That would make a project like the one in the linked article come down to getting a magic module that provided an internet connection...