My way around the issue with the app and its collection is :
Install in a separate profile with empty everything. (So they get an empty contact list)
Install beeper in a different profil and connect WhatsApp to beeper.
Remove all permissions from WhatsApp. There if I need to reconnect sometime.
Oh and using fake number is also a good idea. And yes not as good as selfhosting I know. Signal is an option if you can get them to switch. Telegram is crap.