I found an article by looking up bread recipes : thebreadgeek(.)com/2015/03/make-natural-yeast-scratch(.)html as well as a page on ancient egypt itself, that seems to have valid sources. I’m neither a baker or an egyptologist but I hope this helps! www(.)reshafim(.)org(.)il/ad/egypt/timelines/topics/bread(.)htm

Thank you @ja-khajay!

For anyone interested in making bread without adding yeast (or baking soda) here’s some resources!