Whatsapp: Yeah, I use this a lot for communications. Here not having Whatsapp means basically no texting as no one I know of has used SMS in over a decade now.
When I was visiting Germany in 2019, I installed Whatsapp because it was clear that it was how groups and individuals messaged each other there. Here I find that Messenger provides the same function among groups and individuals, and I haven't used Whatsapp since I got back from Europe. Both free you from a single device which is what happens on SMS tied to a single phone number. Nonetheless many of my contacts prefer SMS, presumably since they are 1) older and 2) have my mobile phone number already.
Actually whatsapp is (for some dumb reason) still tied to your phone number. You can use it on PC by scanning a QR code with your phone, but it is somewhat clunky.
I will say that this seems to be country dependent as when I was abroad, Facebook Messenger seemed to indeed be how people communicated with each other. It's just that in Spain Whatsapp has de facto replaced all sorts of texting, for all purposes.
The only other social media that even comes remotely close is Instagram in my experience and even it gets a fraction of the communication Whatsapp does.
