This means that you need a functional number that can receive written content or calls to turn on WhatsApp. Until now, no tangible rules were given to turn on WhatsApp without receiving a code, neither from official WhatsApp sources nor from unofficial sources.
Of course, you will need to understand a phone number not registered in WhatsApp.
We show you a trick with which you can have WhatsApp on your Android without a SIM card. Sometimes requiring a SIM is a problem if you want to use the same WhatsApp account on two different platforms, or on a tablet.