Fish Patties and chips. Rice and Beans. Spaghetti and alfredo sauce. Salmon burgers and chips. Potato Salad w fresh herbs. Egg salad sides. Chicken and rice or chicken and potatoes. I'd just lean into all different types of salads. Orzo is a nice side, as is bulgur imo. Fresh coleslaw maybe? I'd also lean into green veggie sides like asparagus, broccoli/ broccolini, maybe even buffalo cauliflower (if he likes a little heat). I think Amber mentioned cucumbers yesterday too, there are a lot of fun cucumber spin offs. I think a lot of Asian salads are cheese free too. I like a bit of raw red cabbage in mine as well, adds a world of flavor and texture. But that's all my palette. That might all sound like a pile of shite to him/ you & him.
I'm not really one for root vegetables other than potatoes. But I know loads of people that go crazy with those. Roasting them and doing all kinds of whacky shit with them. I don't want to lead you down some nasty onion, eggplant, parsnip path though. Mushrooms are something people either tend to love or hate. I hate them, he might love them though.
Peas and corn could be a good side too, lots of people tend to like those. Those are fairly benign, like sweet potato I guess.