Lentils! Lentils make a great "ground beef" substitute and work especially well in things like tacos, chili, sloppy joes, "meatballs". So versatile and so cheap.
This vegan
meaty beany chili uses assorted beans and is really delicious.
Beans in general are good for protein and fiber. I love to incorporate black beans, kidney beans, chickpeas, cannelini beans, great northern beans, pinto beans...just about any kind of beans into meals. You can always follow the "bowl" template for a complete vegetarian meal. A bean, a green (vegetable), a grain and a sauce. Want a Mexican flair to dinner? Make a bowl with black or pinto beans, cilantro lime rice, peppers, lettuce, and salsa. Add a little cheese, guacamole and sour cream as you like. You can take the "bowl" is so many directions with different combos of beans, veggies, grains and sauces.
I usually avoid fake meat substitutes, but recently tried the Beyond Meat brand of grilled "chicken" strips. They made really tasty fajitas along with peppers, onions, and a fajita seasoning packet.