So I have a few methods for you to choose from if you want to reduce your screentime.
1. Restrict your apps with the help of a friend. Many phones give you the ability to restrict your app usage to a custom time limit and lock said feature in with a code. Get a friend to make up a code (have them also write it down somewhere in case they forget it) to eliminate the possibility of you just bypassing the lock.
2. Install an app like Beeper. Beeper is essentially an app that allows you to link the majority of your socials and allows you to access all your chats through this app. If you feel like you can't get rid of some apps so you don't lose your connection to your friends and family, this is a very good alternative.
3. Get a dumbphone! Frankly there are so many different types with different levels of "dumbness". For example japanese keitai flip phones have fully functioning android systems, although of course, it's more annoying to use considering the keys and scroller are tiny and more primitive, so you're less incentivized to use them for that (also they're sO cute and customizable). There's also the hisense e-ink phones! Very good for your eyesight, especially if you real books or comic books. Not great for watching videos or moving around (yet), also they're usually in black and white. Ofc they also have fully functioning android. Lastly are the actual stupid ahh phones. The bare-bones.
I understand this might seem daunting and difficult to wean off of, however you can always remember you can access your socials through a PC. Take the time to create a schedule where you access your socials only when you have to, and to be productive. Start living and creating, and then you can also create a more meaningful online existence.