What are you looking for from it? Protein? The firmest tofu you can find or the fried cubes of it you can find in some Asian supermarket. Texture? mock duck or any faux unbreaded chicken or beef (Gardein makes decent ones). Or faux breaded patties for a katsu style curry (Gardein again). Soy beans or chickpeas work relatively well but they don't provide much of a contrast to the other veggies. I've never tried them in curry because there's already rice under it, but Korean sliced rice cakes have an enjoyable chewy texture when cooked.

If you like curry, you might also like a few of the others with similar prep: hayashi rice, brown sauce, or white stew. They come in the same roux form and are just as easy and cheap.

I think last time I did curry, I just added more vegetables. I like for example cauliflower. Added a bit later so it has some texture left to it. Not sure if that goes into karē raisu, but curry sounds like an invitation (to me) to put in whatever I like. Tofu or vegan chicken alternative, probably fits as well.

Tofu? More veggies? Wealthy elite? (don't count as meat because they aren't people) What is your goal here?

In addition to the other excellent recommendations here, soy curls or soya chunks are pretty good alternatives. They're made of dehydrated textured soy that has a very chewy, meaty texture when rehydrated, and will also absorb flavor from the liquid you use to rehydrate them, meaning they can be rehydrated in a vegan chick'n or imitation beef broth, or just directly in your sauce.

Tofu is a general go-to as a meat alternative because of the high amount of protein, the many ways it can be cooked, and for being able to take on flavors well. Basically it's very versatile. Lots of advice online for cooking tofu for a curry. My general advice is to freeze every block of tofu to give it good texture, then thaw and press. For a curry just think about if you want the tofu to be hard and firm, or more tender as this will impact how it is cooked.

I've made it with just the vegetables you mentioned and it was good. If you need something else in there, maybe tofu or mushrooms? But try it with just the veggies.