Thank you for the answer, but honestly I’m very disappointed with him.
Please do not take my response as a desire to offend anyone.
However, it actually turned out that RPI solutions are the most famous microcomputers in the world.
The people who purchase them want to solve a variety of problems with their help, including telecommunications, including VoIP. And the ability of processors quite allow this.
It’s very strange that I can watch streaming broadcasts without difficulty, including in high resolution, but I can’t use the SIP client. Meanwhile, the chipset, as you rightly noted, provides such a technical opportunity.
Really, on what planet do developers live? They brought to the connectors a lot of different signals, but about to brought into a single pin audio input is not thought!
You mentioned customization of the board. And what can be done for this?