You can find legacy driver versions (like v1.2) on the Casio Electronic Musical Instruments Support Page .
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. casio lk 300tv draiver skachat
Windows 98, 98SE, Me, 2000, XP (32-bit), and Vista (32-bit). You can find legacy driver versions (like v1