No idea, haven't touched WhatsApp and don't intend to. :)

That said, the SW will of course lag behind commercial offerings. Just see how long it took for desktop Linux to catch up to the major players. But open source system gives me the freedom to turn it inside-out, get rid of things I don't want (even systemd if I felt really strongly about it), repair what I want - be the owner of by phone and not just a cow to be milked for rent. Nah, I can live without WhatsApp. Or I can get a secondary cheap Android phone for such apps.

Devices are cheap. If you can't live without certain proprietary apps, carry two phones. If you don't want to do tethering for battery reasons, a second cell plan is under $10/mo.