Sure, but the vast majority of sites don't support it, and it's necessary to have explicit support from both client and server in order to perform an ECH negoti

Sure, but the vast majority of sites don't support it, and it's necessary to have explicit support from both client and server in order to perform an ECH negotiation. It can't be performed against existing HTTPS implementations without deliberately enabling the functionality. I would guess that ECH server-side support is still only a few percent of sites at most, although maybe Cloudflare is going to enable it by default at some point? (I don't think they have done so yet...)