I had the exact same Problem.

You need an Android Emulator for your PC, since Whatsapp for desktop always needs to be paired with a phone, then install Whatsapp Business. The Business Version lets you sign up with a landline number. Youll geht a call with the code read to you, and youre done.

If you already have a number, and are planing to keep it, you can just use that, and read the code from your phone.

If you decide to use a desktop app or the web version instead, you will have to open Whatsapp on your phone once every two weeks or it will unpair.