I just have the app in a separate profile right now. Ideally I’d like to run CopperheadOS and have it virtualised or something, but I chose the wrong hardware. I also don’t keep anything very sensitive on my phone is the first place, besides just the data it can passively collect about it’s environment.
The problem with WhatsApp, to be clear, is that the app itself is a closed-source Facebook data hoover. If you stop it from seeing outside data it should be okay. It’s also possible it can be put into a mode where it relays incoming messages after they’re decrypted, but if they ever got caught doing that there’d be a bit of hell to pay, and I can use Wireshark as well as the next guy.