A community-made, unofficial driver for older USB-only Casio keyboards on Mac is available on GitHub and may work for newer macOS versions like Big Sur.

This keyboard will not work with iPad or iPhone because it lacks "Class Compliant" MIDI support, which is required for mobile devices. Installation & Troubleshooting USB Midi driver for Windows 10 - Casio Music Forums

You can find legacy driver versions (like v1.2) on the Casio Electronic Musical Instruments Support Page .

The official driver was originally designed for older Windows versions.