I created a Yocto recipe for libwebrtc in meta-flutter (scarthgap):
https://github.com/meta-flutter/meta-flutter/blob/scarthgap/recipes-graphics/libwebrtc/libwebrtc_125.6422.06.bb

Support will be added to kirkstone and dunfell in the near future.

Also flutter-webrtc plugin support has been added to ivi-homescreen/flutter-auto:
https://github.com/toyota-connected/ivi-homescreen-plugins/tree/v2.0/plugins/webrtc