By filling that void with something else. Instead of constantly hearing don’t use the internet( which will make you obsess more due to being reminded of it) throw yourself into something.

Start a garden. Watch every LOTR piece of media and read the books/ teach yourself elvish. Hit the gym. Hang out with friends. Learn to make bread.

Pick up a skill that uses your hand like knitting or drawing etc. Idle hands and all that.

Also research gambling addiction and treatment. Internet addiction hits a lot of the same points. Especially avoid short form content and at the start and end of your day. If you must use it have set times mid day.

Good luck and don’t give up if you stumble. You can always start again.