I mean I know that I can google it up but I'm looking for a working example. I found some code in github that is obsolete. Also whatsapp requires phone code and qr scan so looks like it's designed to prevent a server-only bridge.
WhatsApp does work, I use it on a daily basis. The bot/bridge makes it easy to log in with the QR code. You need to keep the phone app as you need to open it at least once a month or so.