I was doing some reading on GCC (https://datatracker.ietf.org/doc/html/draft-ietf-rmcat-gcc-02) but was unable to find if this was actually implemented in WebRTC.
Would someone be able to verify or point me in the right direction?
It is implemented here: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/modules/congestion_controller/?q=congestion_controller
The details have changed a bit since the draft was written but you'll find many of the elements described here in the goog_cc directory.