My memory is fuzzy, but I'm pretty sure I did this with WebRTC a while ago. Use RTCPeerConnection in unreliable mode, "peer" with the server, and you should have a UDP-backed SCTP connection. I'll try to dig up my PoCs on this.
Edit: Oh he mentions this, but invalidates it due to the complexity of typical P2P:
> But from a game developer point of view, all this complexity seems like dead weight, when STUN, ICE and TURN are completely completely unnecessary to communicate with dedicated servers, which have public IPs.
I don't remember this being complex (there was some off-the-shelf library for getting a data connection on the server-side), but YMMV.
Edit: Oh he mentions this, but invalidates it due to the complexity of typical P2P:
> But from a game developer point of view, all this complexity seems like dead weight, when STUN, ICE and TURN are completely completely unnecessary to communicate with dedicated servers, which have public IPs.
I don't remember this being complex (there was some off-the-shelf library for getting a data connection on the server-side), but YMMV.