At some point some company has to know the clients age to block the access, thus RTA is the only solution that potentially does this with the optional assistance of the parent whilst not sharing any data. Anything else will require connections to a 3rd party which is still a non starter even if using using magic math that pinky promises not to be reversible meaning someone can put 2 and 2 together to get the persons identification. People have caught on to the shell games.
I will instantly delete my accounts if discord or any service implements this kind of tracking.
There are other ways to protect the children.