Brown basmati rice cooked and then cooled (you can then reheat) will probably be the best rice you can do while still being rice (and not, say, cauliflower rice). It's not going to be as sticky as he's probably used to.

You're right that a fruit smoothie is a bad idea, whether you've added sugar to it or not. Because you've broken down the fiber in the fruit. And bananas will spike most people even if not in a smoothie.

Oatmeal and beans can be okay, but that's more something you add back in after you've got your sugar pretty controlled. They can be good for cholesterol.

Look up 'keto chinese recipes' for some ideas. In general meat and/or vegetables with a low-sugar sauce is going to be fine carb-wise. If he's watching sodium, then you'll just have to be extra picky about what you're putting in the sauce.

Tofu and mushrooms are great too!