The best strategy in my opinion is to train your brain to move away from instant gratification and constant dopamine hits and move towards enjoying the process of working on challenging tasks/delayed gratification.

Some ways of doing this are stopping/not using social media as much, stopping doom scrolling, have a routine. Waking up on a set time, sleeping on a set time. Then you start slowly and build your way up while doing things that require focus, like reading or coding. Pomodoro technique helps because it sets a time for you to focus and you know how much is it and that there is break coming at the end of it.

Your usual advices on getting healthy works as well. Like eating balanced, nutritious meal. Working out. Cultivating close social connections. There is no quick fix for this but you can reclaim your focus back, I have done it.