I use the the Airbnb messaging to start with but a day before they come I'll add them to my contacts list as an emergency/family/priority contact. That way any of their messages get through even if I'm on DND. Then I see what platforms they're connected to, unless they have privacy their privacy settings set. If they pop up on any I'll send them a follow-up message saying that they can contact me on the platforms I see them on if they need to contact me straight away. So far I've used WhatsApp mostly but have also seen:
WeChat, MiChat, Line, Imo, Duo, Skype, and FB messenger.