My 83 year old uncle wants to live alone in his house but the family knows he is not cooking. Any advice?

Order meals delivered to his home.
some of these services deliver once a week, some twice a week

they are just pop into the microwave and instant hot meal.

i am guessing this might be the best solution for him.

There has been talk by my 85 y/o bro of moving back home to his condo. My worst fear is the food thing. He lost so much weight prior to accident and diagnosis at the beginning of the year, and his time in AL has fed him three squares he really enjoys; back to normal weight. I noticed on visits to him he was eating only fruit, sandwich, can of tuna. Just no drive to cook, really often enough I suspect not any drive to eat.
If your Uncle is not suffering from Dementia, and is safe at home, why not check out meals on wheels. Will at least present it at the door. Whether he eats or not is up to him. If he is otherwise safe at home try to help him shop, clean the refrig, and stay independent until he can no more. Trust me, "leaving home" breaks them, and their hearts as well. For my bro he would "rather have just gone at home". And I suspect this is true for most. Talk with him. See what he has to say. Believe what he has to say. Be there for the changes if you are able, as they will come. Wishing you and him the very best of luck.

My mom was younger than that when she stopped cooking. And, I’ve been alone for nearly three months while my husband has been in rehab for mobility issues. I can attest to the fact that doing actual cooking for one person is very difficult. While my husband has been gone, I’ve tried doing a tiny roast, which are hard to find in the stores. I still threw half of it away.

Does he have a microwave and is he able to use it? Instead of buying him food he will need to cook, get the prepackaged meals. They aren’t that bad health-wise. The portions are small and there’s no clean up. There’s no need to worry about an oven being left on since the microwave turns itself off when done. Buy a half pound or so of lunch meats and cheeses.

Every two weeks or whenever someone visits him, monitor the food. Bring some more lunch meat, fresh bread and cheese. He may be cranky, but don’t be afraid of him. The bad food needs to be taken out and the refrigerator or pantry cleaned. He will get over it.

For me, the big concern would not be whether uncle is cooking but whether uncle is eating and, if he's eating, whether the food is safe (that is, not moldy or rotten). It seems as though the person who takes him to the grocery store every two weeks could also help put the groceries away and then throw out bad food as necessary.