You have to ask yourself: what can you actually get away with.
If you’re techy, get a Linux phone. I assume there’s a WhatsApp client, but if not you could bridge to Matrix.
Then you’ll have the option to use a phone, without the addictive qualities of Android/iOS.
Your next best will be GrapheneOS. By default, no Google, so no notifications at all. But that can be turned on and enabled if needed.
Spun it up. Works great. Thank you so much