How to force HTTP/1.1 in specific AJAX request

Question

Background: our server supports both HTTP/2 and HTTP/1.1 protocols.

However, during tests, it appeared that HTTP/1.1 is much faster for files upload

Answer 1

No this is not possible. HTTP/2 is a connection level setting that is negotiated by the browser as part of the HTTPS set up and cannot be overridden for certain AJAX calls nor set for particular paths.

The only way this would be possible would be to host this on a separate domain with a separate HTTPS certificate.