Safe uses for sourdough starter discards during building phase
As long as there is no mold or any "off" smells, any use in which the discard gets cooked (i.e., no raw flour ends up in your final product) should be safe. After all, your starter is little more than a mixture of flour and water, the main ingredients in any number of baking recipes.

The internet is littered with recipes using sourdough discard. A personal favourite of mine are these cookies. If your starter has not yet matured, it is likely that it will not have the leavening power some recipes require. Look out for recipes that include alternative leaveners (such as baking powder or regular yeast), or that won't suffer from not rising (like these crackers). Once your starter is happily bubbling away, any recipe is an option.