The strongest solution to this is to use the web sites instead of the apps. I only have a few apps I really need: all the Google apps, Strava, Garmin Connect, micromobility apps for bike and scooter share, and that's it. Everything else is a website. And none of these apps are allowed to notify. The only notifications I ever get are Apple Pay and Messages. I don't even let the voicemail app (Google Fi) notify because what kind of jerk leaves a voicemail?