DoH client software using HTTP/1.1?

[Christoph]

Hello!

we run a public DoH service that currently supports HTTP/2 and HTTP/1.1.

RFC8484 recommends [1] using HTTP/2 but does not require it.

We see about ~5% of DoH queries coming in via HTTP/1.1, but the DoH
server software we use (dnsdist) will stop supporting HTTP/1.1
so we are wondering whether we should make an effort to keep supporting
HTTP/1.1 via some reverse proxy that talks HTTP/1.1 to these DoH clients 
for some more time to allow DoH clients to upgrade.

Do you know any DoH client software that is actually deployed and used 
in real world that does not support HTTP/2 yet?
We do not have any logs containing user-agent strings.

best regards,
Christoph


[1] https://www.rfc-editor.org/rfc/rfc8484.html#section-5.2
> 5.2.  HTTP/2
> 
> HTTP/2 [RFC7540] is the minimum RECOMMENDED version of HTTP for use
 > with DoH.