This is true, unfortunately. A common way around that is that you must connect both the controller you want to use and an original PS4 controller to the adapter

This is true, unfortunately. A common way around that is that you must connect both the controller you want to use and an original PS4 controller to the adapter. The adapter will forward all DRM/handshake messages to the original controller, but forward the input from the desired one. Unless Sony is now signing every message I see no reason why this approach couldn't be used on the PS5/DualSense. That said, my cursory search didn't reveal a working PoC.