Loads of things.
Paella, various stews / casseroles / tray bakes/ kedgeree.
I add veg into cottage pie so it doesn't need any veg on the side, frozen peas and corn, carrots etc.
I cook smoked fish with rice in a 50/50 orange juice and water mix, I sometimes add cashew nuts and again a handful of frozen veg. It all goes into the rice cooker.
One for the slow cooker.
Pork ribs - where they are actual ribs not separated - place round the edge of a slow cooker, add choice of veg but I always include butter beans, add passata, seasoning and boiling water.
After a few hours the cartilage will have melted into he sauce and you can pick out the bones, leave for another couple of hours, I tend not to use potatoes but I'd usually have some crusty bread to go with it.
If you do want to cook sides then think about ones that will hapily sit for a while once made / cooked.
Salad s an obvious one but also baked potatoes - they take about an hour in a conventional oven and will happily sit for another hour if you turn the oven down.
If you get a steamer you can cook meat or fish wrapped in foil alongside steamed veg.