The following post is based on the assumptions that 1. upstream HTTP/2 support is not available in nginx at the moment, and 2. said feature is not firmly excluded from nginx's future road map :)

We've been internally using an nginx patch (authored by me) which provides this feature in our nginx instances that front-end etcd servers.
Please let me know if this patch can be a candidate for review and potential merge.

In case the answer is yes, a heads up: said implementation has been subject to a few 'compromises' due to internal deadlines, so I might need a fair bit of technical guidance/discussion to iron out some design/implementation issues.