I've found having draconian phone blocking rules helps. I use Jomo

https://jomo.so

but I'm sure there are other competing products.

Roughly, you can classify apps in your phone to things that

1. are fundamentally fine (various bank/payment apps, messaging app, map apps), and

2. are known time wasters (social media)

you then just block the time wasters. you can configure it so that to edit the settings of the app, you have to enter some 150 character randomized code. it is very annoying to do.

this is the point though. there are other ways you can add friction to using your phone. setting its display to be black and white makes it much less enjoyable to use, for example. if you add in enough friction (and stick with it over an initial "hump"), you'll findi yourself reaching for other options.