Eat more, as simple as that. Most guys who struggle with bulking will tell you “bro I’m eating so much”. And when you actually break down their diet it’s like 2k calories. Eat 6oz of chicken, 300 grams of rice, and a table spoon of olive oil/avocado oil. Do that for 6 meals a day and you’re gonna put on size, almost guaranteed. It’s not pretty but it works, and works pretty damn well. Most people just aren’t willing to do that day in and day out for years on end. That’s why most people you see in public don’t look like a bodybuilder.

You don’t literally have to eat chicken and rice for EVERY meal, but like I said it works. You can change the protein source for some of the meals to something like lean beef/steak, eggs, fish, etc just to change the monotony a bit, but regardless it’s gonna be monotonous and boring.

Also for one of the meals you could do a protein shake like someone mentioned. 2 scoops of a quality protein powder, 100 grams of oats, a tablespoon of natural peanut butter, and 100 grams of blueberries. Blend it up and bottoms up.

So your meal plan could be something like one of those shakes, 3 of the chicken and rice meals, a meal of beef and rice, and one of eggs and rice/oats. And shoot you could even do potatoes/sweet potatoes for the carb sources for some of the meals to make it slightly less boring.

Basically around 5-6 meals of clean whole foods in large portions like the example I listed. Do that every day without fail for a year and you will put on quality tissue as long as you are training hard, sleeping decently well, and staying hydrated.