What can be used to thicken chili other than masa harina?
There are several ways you can thicken Chili than adding Masa Harina:


Add another thickening agent: flour and cornstarch are both widely used, you can also try other flours like graham flour, chickpea flour, or arrowroot. Note that if you use flour you'll want to fry it in oil or butter or risk a raw flour taste in the dish
Add refried beans: this adds thickening and a richness. It does dilute the spices some so you'll want to make the chili more powerful to compensate
Cook it down: Why add a thickener when simply simmering with the lid off will do it for you? It takes some time (an hour or so depending on the water content of the ingredients you add), but it will concentrate the flavors and give you a nice, thick chili without any additional ingredients at all