Great question! You can substitute potato starch for tapioca flour at a 1:1 ratio, so for your recipe you can use 1/4 cup potato starch. That said, there are a couple small differences to be aware of; potato starch absorbs a bit more moisture, so your batter might be slightly thicker.
It can make baked goods a little softer and more tender, whereas tapioca adds a bit more chew.
If your batter feels noticeably thick, you can add 1–2 teaspoons of extra liquid (milk, water, etc.), but most recipes work fine without adjusting.
I have a recipe for a chocolate almond bread made with almond flour that calls for a 1/4 cup of tapioca flour what would the ratio be for potato starch as a substitute as I don't have tapioca flour? TIA