If I couldn't get out with my kids and they needed to burn off some energy I used to play Simon Says with them or have challenges - can you walk to the end of the room and back with a balloon between your legs, can you run with it. Can you hop on one leg to the end of the room and back, can crawl, pretend to be a snake etc combos - can you jump up, take 2 giant steps, 4baby steps, then bunny hop etc- make silly stuff up. My kids also really liked playing in the bath, so I'd make it bubbly or add food colour and let them have whatever toys they wanted in it. Shark grabber and fishing rod games are good and can be used over the bath as well as in it. My kids liked putting on their swiiming costumes to pretend it was a pool!
Structure the day and plan the activities the night before - breakfast, an activity, a snack, an activity, lunch, film/programme, activity, books, computer game etc.
I'd let him make as much of the food as he can - butter the bread, cut the sandwiches, push down the toaster etc. My DC used to like indoor picnics sitting on a tablecloth or blanket, so it was easy to fold up the corners and shake all the crumbs into the bin and they could prepare the food themselves and wash up. I also used this playing on the blanket/sheet method with bitty toys such as Lego and playmobil or small cars. Get in some cheap craft kits if your DC likes that, maybe get a toy he has wanted ( if you can afford it) especially a building type kit toy.
Book series are good if your DC can sit and listen or a series of films. My DC used to like the Pokemon films and Harry Potter ones. You can do more than one a day, have a binge or eke out throughout the week. My son only liked non fiction so he liked DK find out type books and I used to keep some of those in stock.
Children ususally love attention from a parent so ask questions to get your DC talking - really listen, prompt for more info and praise. Keep it going.They love it! Examples:
https://www.newhorizonacademy.net/20-questions-to-ask-your-kids-to-get-them-talking/