Encrypted Client Hello, which is what eSNI developed into, is an active draft for the TLS working group. If you have relevant expertise I'm sure that the group would be happy to have you, in particular if you have any insight into how to achieve goals like Don't Stand Out while also keeping ECH as simple as possible.

https://www.youtube.com/watch?v=AIDnO_QB64A is the most recent interim video conference meeting on this topic.

I expect that during 2021 they'll pin down the more controversial parts that remain to be done.