Moving schools is a big adjustment and some kids take longer to settle in than others. A year is still pretty early honestly, especially if he was leaving an established friend group behind. That said, there's a difference between taking time to adjust and completely withdrawing. The fact that he's not interested in clubs or sports is worth paying attention to, because those are natural places where friendships form. Some kids are just introverts and that's fine, but at 16 you want to make sure he's not isolating himself out of anxiety or depression rather than just preference.
I'd suggest having a casual conversation with him about whether he actually wants friends or if something's holding him back. Is he anxious about approaching people? Does he feel like he doesn't fit in? Or is he genuinely content doing his own thing? The video games alone part isn't inherently bad, but if it's *instead of* any social interaction, that's different than if he's also just talking to people online or hanging out sometimes. You could also nudge him gently toward low-pressure social stuff rather than competitive sports or clubs - like gaming groups at the library, online communities around his interests, or even just suggesting he invite one person to do something.
If he seems depressed, withdrawn, or unhappy about being lonely, then yeah, I'd be a bit concerned and maybe worth talking to someone about. But if he seems genuinely okay with how things are, pushing too hard might backfire. Some people's social circles expand naturally once they find even one person to connect with, then things snowball from there.