Where do you get your protein?
Protein originates in plants. Animals assemble theirs from what they eat. Pulses, soya, grains, nuts and seeds supply all nine essential amino acids, and deficiency is rare in anyone eating enough food.
Meat, eggs and dairy deliver complete protein in dense, easily absorbed form, which is why people have relied on them for strength, growth and recovery for as long as anyone can remember. Plant foods carry less protein per bite and are often low in one essential amino acid or another, so a vegan has to eat more, combine foods deliberately and keep careful track just to reach what an ordinary omnivore gets without thinking. For growing children, pregnant women, older people losing muscle, or anyone who trains hard, that is a real risk to their health, not a minor inconvenience.
Every essential amino acid is synthesised by plants or micro-organisms. Animals obtain them the same way we can: by eating plants. Lentils, beans, chickpeas, tofu, tempeh, seitan, peanuts, oats and wholegrains are all substantial sources, and the major dietetic bodies (the Academy of Nutrition and Dietetics, the British Dietetic Association, Dietitians of Canada) state that appropriately planned vegan diets meet protein requirements at every stage of life.
In high-income countries, protein deficiency is overwhelmingly a consequence of eating too little food overall rather than of avoiding animal products. The question deserves a straight answer once, and the answer is unremarkable: beans, lentils, tofu, nuts, bread.
Asking a question that builds in an unproven assumption, so that any direct answer concedes it.
How it applies here: The question presupposes that protein is hard to come by without animal products. That assumption does all the work and is never stated outright, which is what makes it awkward to answer in a sentence: any direct answer appears to concede that there is a problem to solve.