Settings when configuring http/2 for the client side only

BIG-IP translates by copying the HTTP generic headers that are common between HTTP/2 and HTTP/1.1 to the HTTP/1 side. There's nothing much special. If you're encountering an error in the connection, the best thing to do is to capture it using Wireshark. Here's an article I wrote on how to decrypt TCPdump/wireshark packet captures: https://community.f5.com/t5/technical-articles/decrypting-tls-traffic-on-big-ip/ta-p/280936

Once you decrypt the HTTP/2 side and concurrently capture the HTTP/1.1 side, just look for the error message and maybe share it here.