Eat as a family- let him observe other people eating/enjoying the food. NOT in an over-the-top “Mmm I love XYZ” way, but just the normal course of the meal.
Have him help prepare the meal. Can he cut up soft carrots? wash some veggies? Pour/Mix a marinade? Shake something to mix it up, then put into the pot? This helps my daughter more than anything become interested in trying what I serve.
Put it on his plate. Even if he doesn’t eat it “you don’t have to eat it, but it needs to sit on the plate like Mommy/Daddy,” it sits there, and he becomes familiar with how it looks.
Don’t force the issue; serve what you serve. Try to include at least one side he will eat; don’t cook a separate meal for him. If he doesn’t eat dinner, he may be hungrier for the next meal, so keep that in mind when serving the next meal.
I’ve used that approach with all my kids, and they are all very good eaters. We ignore the “I don’t likes,” we do NOT force trying it, and we are as no-pressure as we can be.
You are not hungry all the time, I assume- it’s fine for him to eat less/more at different times, too, or not be in the mood for something in particular
Y’know I’m remembering a phase with all my kids around the 20-26mo age where they were “picky,” and we ate a lot of spaghetti/casserole (for meat), and I’d feed them (only at dinner) at the end, if they were willing to let me. They were getting frustrated with silverware, but didn’t want to use their hands, and would just sit there/say they were done. COLD hardboiled eggs are good for protein, too, esp if they are just young enough they think it’s cheese…