My 3 year old is a mega fussy eater, but one of her favourites is egg fried rice, which I use brown rice for, and can sneak in really small chopped white fish/chicken/ham without her noticing, lots of veg (peas,sweet corn she likes, grated carrot, onion, courgette etc she doesn't notice), it's a winner and a regular meal.
She also is a big fan of mash, and will accept any mash, so can shove any root veg in as long as it's mashed, things she wouldn't eat plain. I also get away with sneaking finely chopped fish/chicken under the mash on her spoon. This also works with fish cakes, again can shove other grated veg in and get away with it.
She loves Greek yogurt with 'jam' to stir in herself which is any fruit I have just cooked down in a pan until compote consistency, no added sugar which is much better than premade fruit yogurts.
We cook and bake quite a lot together, and I try to get her involved in all cooking as much as possible, it definitely makes a difference with her trying foods she's helped make. She loves cooking together, it's lovely time to spend together.
I've got a good healthy oat and banana muffin recipe that you just shove everything in a blender and cook, she loves making it together and the muffins freeze well and defrost in 30 secs in the microwave so make a great quick breakfast with some fruit or a snack. (Happy to share a link to it if you like).
Homemade pizza is a winner too, with loads of veg blended into the tomato sauce, sweet corn and pineapple etc for toppings.
She has been fussy since about 18 months old when we had an awful time with teeth, it can be absolutely soul destroying at times. She seems to be finally accepting more things, in the last couple of months sandwiches, filled rolls, broccoli and ham have all been added to her repertoire, which seems so pathetic, but to us is a monumental step forwards! Keep trying things, you never know when they'll take a shine to them!