Preheat your oven to 350 F. Grease a 9x5-inch loaf pan and line it with a strip of parchment paper.
In a medium bowl, whisk the 1 ½ cups oat flour, ½ cup almond flour, 1 teaspoon baking soda, ¼ teaspoon fine sea salt, and ½ teaspoon ground cinnamontogether. Stir in the 1 cup semisweet chocolate chips.
In a large bowl using a handheld or stand mixer fitted, beat the ½ cup unsalted butter, ½ cup light or dark brown sugar, and ¼ cup granulated sugar together on medium-high speed until light and creamy, about 3 minutes. Beat in the 2 large eggs one at a time. Scrape down the sides of the bowl as needed. Beat in the 1 ½ cups mashed bananas and ⅓ cup plain Greek yogurt until combined.
Reduce the speed to low, then beat in the dry ingredients until just combined.
Pour and scrape the the batter into the prepared baking pan, using a rubber spatula to smooth the top. Rest the batter for 15-20 minutes, or while the oven preheat. Place the bread in the oven and bake for 60–65 minutes, until the top is browned and a tester inserted into the middle of the loaf comes out clean. Cool the bread in the pan set on a rack for 1 hour, then turn out of the pan to cool completely before slicing.
Notes
Use the right flours. Yes, you can absolutely use a 1:1 gluten free flour blend here (and if you do, please use my homemade gluten free flour blend!). But I will lodge an argument in favor of using the combination of whole grain gluten free flour + nut flour in this ratio. I've tested it so many times, and it always produces a tender, moist, yet sturdy loaf every time.
Make sure your bananas are ripe. I cannot overstate this! The browner your bananas are, the better (obviously don't use bananas that have mold on them). This means that they are sweet and soft, and will seamlessly blend into the batter. If you don't have ripe bananas, just wait to make this recipe until you do. There's no compromising.
Cool the loaf completely. While gluten-free bakes are by nature a bit more fragile than those made with wheat flour, an easy solution is to let them fully cool before slicing. A little magic happens during this process in which the crumb tightens, making it just as sliceable as a regular loaf of banana bread. But don't rush it.
Make it a little extra. Add two teaspoons of pure vanilla extract or vanilla bean paste, fold in some chopped pecans, make a brown sugar cinnamon swirl, or the oat streusel from my peach bread recipe (use oat flour for the ap flour) to sprinkle over the top.