That's good news, the WebRTC world is too much of a libusrsctp monoculture to my taste at the moment. Don't be surprised if you find some interesting edge cases in browsers as you stray from the beaten track :)
Yipes! That's good to know about, thanks. At the same time, I've also been surprised at how lenient the browsers are at accepting associations from my incomplete implementation (e.g. without the required SCTP extensions, etc.).
I can confirm you can get data channels to work with zero SCTP extensions, I only added them afterwards!
One implementation (libusrsctp-based) you might want to interop with is rawrtc. Like aiortc's datachannel-cli example, it features copy-and-paste signaling which makes testing easy.