I'm in Canada. My s/o once had an employer force their staff to use WhatsApp and it was horrible, lol. The notifications were constant and the whole getting work stuff while at home was annoying. But she never had that happen before or after that one employer.
I've never had an employer use WhatsApp, they communicate by text if I need to be reached when I'm not working (rare for me), or email/Teams if I'm at work.