I share your woes regarding WhatsApp; my family overseas uses it, so I have to use it when visiting them, and I also had to do the weird workaround of creating a Whatsapp URL with the destination phone number, and then opening it in the browser, and then having it redirect me to the app.

Oh, I forgot about this, yeah, you can use the links that webpages post to workaround it. Quite annoying though, I think I only used it once.

Here's an example link,

https://api.whatsapp.com/send?phone=5551112233