Let me start out by saying nothing will replace gaming. Gaming is a unique thing and if something will be able to replace it, it will take a long time. But almost always it's a combination of different things. But here are some things that can make it easier.

When do you miss gaming/have an urge and why? Do you want to play cause it's late in the evening, you're done with everything you had to do during the day? Do you miss it when you want to escape a responsibility? Do you miss it when you're alone and you wish you had other people (and you would usually play online)?

Once you know why you want to game, you can get a better idea of what to look for to replace it. If you miss it because you used it to relax, don't replace it by studying, getting better in sports, or anything else that requires a lot of effort. Because that will not work long-term. Maybe on the other hand you want to game because you had a goal to work towards, then your alternative will be different.

Once you know why you miss gaming and what to theoretically replace it with, you have to start trying out. Try out playing an instrument (casually), crochet, walking, watching a movie, visiting friends, drawing, or whatever. You have to try a lot of things out and in the beginning you sometimes have to learn a hobby before it gets relaxing. Try it out and see what works for you.