I'm using https://github.com/spantaleev/matrix-docker-ansible-deploy and I can't recall off of the top of my head, but I'm pretty sure out of the box the coturn server will make webRTC "just work". I also explicitly made sure jitsi was disabled to make sure it wasn't using it, and yeah, this ansible playbook is game changing. I tried to run Matrix 3 different ways before giving up and using the playbook.