Maybe get him involved in the picking or buying and then preparing/cooking process. I find if they feel like they get the choice or they’ve helped they are more likely to try new foods..

my 3yo is the same, but i have just come to the conclusion that all I’m doing is stressing myself out worrying about it. And it just put a lot more pressure on me that i didn’t need. so i now rotate the three dishes that he will eat. i occasionally throw something new into the mix, but if he doesn’t eat it, then i just shrug my shoulders.

Just dont tell him what hes getting and then put on the dinner table at dinner time or you can hide veggies in your cooking

Getting creative with food serving, as already mentioned, is a good place to start. Also letting your child help prepare the meal is encouraging. Also growing your own veggies to cook is good, a bit extreme but gets kids involved with food from the start

We make our food like art ie spaghetti in the bowl, spread the sauce over it then carrot rounds for eyes a potato cube for nose and spinach formed into.a line for mouth. Be creative and let your child help.