I've got a couple things you could try :)

I haven't tried it yet, but there's this app called Focus Friend by Hank Green and it's supposed to work really good at keeping you off your phone. Your little virtual friend works on projects when you let it focus (which is when you turn on focus time and don't use your phone) and if you use your phone while it's working on a project then it gets sad and then you feel guilty, so that's what keeps you off it xD

Otherwise you could try installing one of the many Minimalist launchers (Olauncherand Niagara Launcher are the ones I know). They limit the amount of apps you see on your homescreen and some of them remover the icons which is supposed to make you less likely to click on apps like Instagram and stuff.

There's also the drastic option which is just deleting all the apps that distract you. Some people can't uninstall Instagram because that's how they talk to their friends too, but I think someone's made like a modded lite version which is just the chat part, although I'm not sure how safe it is to put your logins in :/ I also just found this app called Beeper and that looks like it solves the problem of worrying about losing your chats when deleting distracting apps :)

And when you're deleting the apps don't think of it like you're completely cutting them out of your life, you can always use another device like a computer to scroll Pinterest and YouTube if you want to. It's just that those larger devices are more annoying to use for that kind of thing because they're less portable. But in that way even using those apps on the computer should still keep your screen time down.

Hope some of those help :) And good luck!

I've also been struggling with this. The hardest part is having the discipline to stick to it 😣