

I suggest installing something like e/os which is phone without google and tracking. You somehow have to make sure that the hardware itself does not communicate outside but at least with a secure OS you are introducing the security issues by installing WhatsApp for work
I know that e/os is based on another degoogled os but i forgot the name
And you can put it on an up to ~8 year old phone so its good for the environment too
not graphene but i know the company Murena offers phones of different vendors with i think e/os, maybe other OS too