Attend a 10-day vipassana retreat. They are donation-based and all over the world.

https://www.dhamma.org/en-US/locations/directory

This will bring back + tremendously improve your attention span, in 10 days, guaranteed.

Once you leave the retreat, you will encounter the same environment and habits which robbed you of it. Which you will need to address.

Knowing that social media is being intentionally weaponized to extract attention from its users is helpful as your attitude toward social media and internet usage is likely a big part of it.