[berti]

> Firefox supports it

Only if you use their built-in DoH resolver. The public keys for ESNI are distributed by DNS records and as I understand it there's a bunch of work to be done for Firefox to retrieve these records from classic DNS servers. That work has been classified P5 (we won't do it, but might accept patches)[0].

[0] https://bugzilla.mozilla.org/show_bug.cgi?id=1500289