Want to know how this tech works and need some GitHub projects based on this technology.
You can try this: GitHub - 0perationPrivacy/VoIP: Web Base Telnyx/Twilio VoIP Interface enabling SMS, MMS and Voice calls using the providers API Keys and self-hosting the application..
But I suggest you try Skype and WhatsAPP firstly.
I set up a small system for a side project with a couple of friends and it worked surprisingly well once we figured out the configs. Later, I got some exposure to call center software that ran on top of it, and that made me appreciate how open source VoIP tech can scale.
Was curious about this too and found a few GitHub projects that handle text messaging across SMS and apps like WhatsApp. Tried one for a side project — it let me set up quick notifications from a simple script. Worked surprisingly well and gave a good base to tweak.