How to check if a VIP supports http/2

You can check by issuing a cURL command to the virtual server (this can be done directly from the BIG-IP's bash shell)

run util bash

curl -IvLk --http2 https://<FQDN>

If you see the following in the result output, then this means that the virtual server is not configured to support HTTP/2. You will need to create an http2 profile and a compatible client SSL profile (httprouter profile and server SSL profile will be needed too if you want HTTP/2 Full proxy) and apply it to the virtual server.

ALPN, server did not agree to a protocol