I’ve been doing our laundry with soap nuts.
They grow on trees. They’re dried shells of a fruit.
They look funny and smell funny, but they work pretty well. The laundry comes out smelling clean and feeling soft. Even my line-dried bath towels are less crunchy. They’re almost soft. And they smell like clean, line-dried, sunshine baked towels.
You tie a few of these into a little cotton bag, and put them in the washing machine. They release a mild, natural detergent into the water.
From what I read on the internet, they work better with warm water than with cold water, and they’re less effective if you have hard water. We have normal water, and so far I like them.