https://gitlab.torproject.org/tpo/anti-censorship/pluggable-...
…in case anyone else needed a link.
Thanks. That README is a bit out of date from when the project just implemented a single transport, this is more accurate[1]. It's what's used in the latest Tor Browser.
Also, allegedly, MAC spoofing of already authenticated clients can bypass many of these paywall-gated hotspots :)