The solution is to create a new profile. You cannot add new entitlements to an existing profile. You may need to unlink the profile from any apps before you can delete it and replace it.

I am experiencing this same HTTP 500 issue when requesting driver kit entitlements exactly as described. filed case ID 102830620344.

[message to moderator] I accidentally marked my own reply as accepted answer. Can you undo this action

For clarification , the "spoofed" hardware is just a simple STM microcontroller that is flashed to impersonate the descriptors of the real USB hardware, with the key difference that I removed the CDC-ECM descriptor.