It's harder to do it on a vegan diet if you don't eat high protein foods, and those foods might be novel to you, sure. But you said "It’s hard to get enough protein from a vegan diet", not "I was unwilling to eat the food". So of course I'm going to step in.

Protein density isn't all that different, but seitan and tvp are even more dense per calorie.

- extra firm tofu 14g protein, 130 cal. 0.11g/cal

- tempeh 51g, 510 cal. 0.10g/cal

- chicken breast 27g, 184cal = 0.15g/cal

- chicken thigh 28g, 240cal = 0.12g/cal

- seitan 21g, 106cal -> 0.20g/cal

- tvp (soy chunks) 50g, 330cal = 0.15g/cal

TVP is cooler than it seems if you were to google it. You basically treat it like dried ground beef in a bag. It's also ultra-cheap. For example, you'd dump it into a bolognese pasta sauce instead of ground beef and it comes out the same.