Try 1.5 aspirin to 2 gallons of water: https://www.plantea.com/plant-aspirin.htm
Vinegar seems to be good for just about everything, but I couldn't find anything online to support it helping seed germination.
My soil is just a touch basic, so it would probably help me. This might be good for several plants with different concentrations in each one.
I've heard of using milk one time on peppers, but as it will likely sour, that's one I'd use outside.