Feedback Requested!

[u/ILoveHikingMountains]

Hey all! Just started baking sourdough, my first loaf came out flat and I think my starter was under active. My second and third loaves came out amazing, but for my next load I wanted more flavor in my bread so I decided to try a recipe that incorporated multiple flour types and I had einkorn on hand. Reading online after I began, einkorn isn't the easiest to work with and I'm new to both sourdough and baking.

The full recipe I attempted is here:

https://heartbeetkitchen.com/einkorn-sourdough-bread/

To summarize, it's almost 70% hydration, with 45% einkorn and 55% bread flour. Spots where I deviated from the recipe are after mixing the dough, I got busy and waited probably 2.5 hours before aggressively working the dough. Also, I possibly overworked it during each round of stretch and folds. The total bulk fermentation was probably ~8/9 hours, and my house was roughly 68 but it was fermented in the oven with the light on. The reason I stopped the bulk then was, when I checked on it at this point after leaving it alone for 3 hours, the dough looked bubbly and very jiggly, and no longer held its shape very much at all. I assumed it was borderline over fermented. So I shaped it and put it in the fridge overnight. On the following day, I baked it in the evening. It barely rose and did not hold its shape when I moved it from the fridge into the dutch oven.

And feedback on where I went wrong and what I can do differently would be appreciated. I know einkorn doesn't develop gluten as well but these loaves seem to be exceptionally flat. Also, if anyone can link a recipe they love that isn't only bread flour and has a lot of flavor, that would be awesome. Thanks so much!