Review on 🔌 Club 3D CAC-1510-A Dual Link DVI-D Adapter with HDCP Off - Compatible with Apple Cinema Displays, 3840x2160@30hz, 2560x1600@60Hz by Vincent Pavelko

You can make your old 30" Apple Cinema Display work! This adapter did the trick (and after I bought two other brands). Finally success. As mentioned before, you just have to click on an option in System_Preferences->Display to enable the native resolution of 2560 x 1600. See photo. And since the adapter goes from USB-C to dual-link DVI, you no longer need another Apple Mini DisplayPort to Dual-Link adapter that requires a USB-A connection for power delivery. Now all you need is a USB-C port and a DVI port from the cinema screen. (I haven't tried the built-in USB hub or Firewire ports on the display.) The power button on the right works, too. The brightness control also works. However, there is no user feedback (white gradient pop-up). I suspect MacOS (Big Sur in my case) is no longer providing this user feedback as the monitor is unsupported. But I don't care, the display dims and gets brighter when I want it too.