As part of #ISRG's work towards memory-safe infrastructure for the internet, @cpu has opened a merge request that implements TLS ECH support on the client side:
https://github.com/rustls/rustls/pull/1718
We agree that "the ECH spec is very challenging to implement and required a lot of trial/error" and we are working with #DEfO to help implementers. Please reach out if that is you:
https://defo.ie/#contact