Like you said PROTEIN POWDER... it's protein in powder. You can eat chicken, beef, pork, fish, eggs, lamb, duck, rabbit... any kind of meat you like. It works the same way.
because of the heavy marketing and adveritising people think that you need a protein powder to gain muscle. that is a myth bro.
it is the same myth that you need gatorade to hydrate, or eating subway will shed weight, or that drinking beer gets you blonde bimbos in bikini's.. it is clever marketing and we are very naive species that fall for it
i have had protein powder probably 5 times total in the last 20 years. and last i checked i'm still alive. i would actually argue that protein powder is counter productive and you are way better off without it because it is so hard to digest