That isn't how dopamine works. If you have ADHD you require more stimulating activities in order to get a satisfying response basically. I don't think a feature phone will fix the problem. Possibly gamifying your ability to not go to those things on your smartphone might be a better plan. Figure out the situations in which you pull out your phone and try to be mindful of those situations and change The situation or your response to it.

You said you went to keep your iPhone at home and put your SIM card in a dumb phone. So does that mean you want to take your phone to work or when you go out? What were the situations in which you pulled out your iPhone and you mindlessly would browse the internet? Are you a coder and that was what you would do when you would wait for a compile or something? Any kind of downtime you would pull out your iPhone like a cigarette smoker would take a smoke break? Try to figure out those situations and come up with alternate activities to do. Once you figure out those alternate activities try to make those alternate activities have the lowest barrier to entry. Obviously pulling your iPhone out of your pocket or inches away from your desk is a whole lot easier than getting up and taking a break and taking a walk for 15 minutes or whatever.

I get your point, but I figured it would be easier to just not have the temptation than try to escape it. I favor minimal solutions that work (even if they don't fix the root cause) over things that require constant willpower.

Yes, I take my dumb phone to work, which means my relatives can only phone or text if they want to join me.

Here's a thought. I got a new phone and transferred zero apps over to it from the backup. I only download an app as I need it.

Today's experiment: Hold down the safari app icon and see what happens. The icon has a minus sign at the top left corner, meaning that it can be deleted. In earlier versions of ios, you couldn't delete Apple preinstalled apps.

No, I didn't delete it. I surf in moderation, mainly because the screen and virtual keyboard are too small for me to use for more than a minute or two when away from the computer or ipad. (which have real keyboards)

If you're addicted to your phone and you want to quit it maybe it's a good idea to use a dumbphone with a shitty UX. Otherwise you're going to get addicted to your dumbphone.

There is nothing to do on my dumb phone, not even games, so hopefully I don't feel the need to check it every 5 min :)