The ring sidetone is sent by the network of the person you are calling; it isn’t generated on your phone or even by your carrier. Many carriers have stopped sending it.
As I already posted in this thread:
Going back to copper wire landline, when you made a call you wouldn’t hear the ring sound until all of the switches closed between your line and the switch for the number you called, and it meant that the connection was successful, and sometimes there would be a delay, as there were a finite number of wires and switches.
With cell phones, it isn’t that different; when you make a call the switch for the receiving end has to find the mobile phone you called; it could be anywhere in the world. It has a hint, because cell phones periodically contact the network and say “here I am”, so the called carrier first tries the tower that received the most recent “ping”, then tries towers around that one moving further out until it actually finds the phone. Until it finds the phone you hear silence; when it connects you will hear a ring sound sent by the called network switch. But if the called user answers immediately you won’t hear the ring.