I am using Nginx version 1.20.1.
I am having a problem because of the conversion of headers to lowercase.

Ex: HeaderTest -> Headertest

I have no control over the applications going through nginx. They use case-sensitive headers and cannot change.

What is the way to prevent NGINX from converting the headers of an exchange?

I know the RFC rule, but I do not do HTTP/2. My partners used F5 before and did not have the problem.

Thanks for your feedback