A couple months ago I went through the hoops of getting anbox set up and working (which I confess involved a lot of mucking around with containers and package versions) and it was .. better than I expected?
WhatsApp and several apps besides installed and opened up fine, and first impressions were that it was surprisingly smooth, given how positively ... anemic the Pine's SoC is. Not pleasant, but definitely usable.
Unfortunately at the time, a bug in the software keyboard and wayland meant that all keyboard input was mangled, so I could never get as far as actually setting up whatsapp and actually testing it.
I remember seeing a month or so ago that Purism apparently fixed the bug in their software keyboard, so now it should work? I've been out of the country though, and haven't tested it yet.