I did a little bit of further investigation, and I’m putting the information here so it may help other AlphaTrack owners.
The AlphaTrack is a USB device but it is not a USB MIDI class-compliant device. This means that, if you plug it into a computer on which no AlphaTrack drivers exist, there will be no AlphaTrack MIDI ports created.
Without AlphaTrack MIDI ports, there is no possibility of using the device, not even by creating a custom MIDI Remote script.
The AlphaTrack MIDI ports are created by the AlphaTrack proprietary drivers, which are almost 20 years old and no longer supported.
If the AlphaTrack drivers are already installed and working on a Windows 10 machine, they may survive an OS upgrade to Windows 11 (thanks @planblue )
An attempt to install the AlphaTrack driver on Windows 11 will result in an error (“Can’t install on this version of Windows”, however it does copy the drivers to the location “C:\Program Files\AlphaTrack”. You can then plug in the device, and in Device Manager, locate the AlphaTrack device, and in Properties | Driver, choose Update Driver and browse to the location of the drivers above.
The final piece of the puzzle is to copy the AlphaTrackCN64.dll to “\Program Files\Common Files\Steinberg\Share Components”, start Cubase and configure the AlphaTrack in the usual manner (also thanks @planblue).
The result is a perfectly working AlphaTrack in Cubase 14 on Windows 11!