If you strongly prefer a standalone app, here is how to get a on macOS 10.15.7.
WhatsApp Web is a browser-based version of the popular messaging app WhatsApp. It allows you to access your WhatsApp account on your computer, making it easy to send and receive messages, photos, and videos on a larger screen. whatsapp web mac os 10.15.7
Now you are fully operational. You can send/receive messages, voice notes, documents, and images up to 2GB (compressed) on macOS 10.15.7. If you strongly prefer a standalone app, here