No updates to post #20 so far (https://forum.x-cart.com/showpost.php?p=410784&postcount=20)
. I'll keep you updated about next steps.
Unfortunately, we cannot create a configuration file for Nginx that would work on any server. We have only *examples* on the basis of which the administrator can configure own server.
Regarding post #23 (https://forum.x-cart.com/showpost.php?p=410819&postcount=23
I'm not sure we can understand the problem remotely. Many of our developers are working with Nginx and X-Cart 5.4.0.x. The default LAMP stack also works well.
But all above not a strong argument I want to help, could you please provide more details, configurations files etc.
Thank you for the feedback, it helps us build a better product.