I often leave the house without my iPhone. Here is my full stack:

- Ask wife to set up screen time passcode and not tell me

- Block social media and other distracting websites in Screen Time

- Set a 1 minute time limit on distracting apps

- Keep the phone in the garage as much as possible

- Get an Apple Watch cellular so that I can still communicate with people, make payments, get directions etc when I am out and about

Not a perfect dumb phone but this has helped me reduce usage tremendously.