Question: Prerequisites and how to build `curl` with ECH support

[Daniel Stenberg via curl-users]

I would like to know which SSL libraries support ECH (Encrypted Client
Hello) and how to build a `curl` which supports ECH. I currently have Quiche
and BoringSSL; however during build time it shows an error that ECH is not
supported and ignored. Would you please tell me how to solve this? It would
be really appreciated. Thank you very much.

curl does not support ECH yet.

Niall O'Reilly works on it and he posted a "roadmap" almost a month ago on the
curl-library list: https://curl.se/mail/lib-2021-02/0051.html

That roadmap is here:
https://github.com/niallor/curl/blob/ECH-reset/docs/ECH.md

I'm sure he'll appreciate all the help he can get!