I want to reassure you that information seeking is a very common form of self-medication for ADHD. I do it myself, and overall I think it helps rather than hurts. You can use it as scaffolding to expand his horizons — encourage him to do it outside in the yard (sunshine helps) or in a coffee shop or a bookstore (extra browsing!). You can also give him something specific to research, something that benefits you (doesn’t have to be big — what TV should we get? what’s a good restaurant for Indian food? etc.). A bit of acknowledgment and a feeling of usefulness can go far.
I also had a rocky start at the university, until I realized the “university diet” was a big problem for me. I really need protein at every meal, and a candy bar or alcohol on an empty stomach would send me in a tailspin. Maybe that’s an area you can help him with.