Natural clothes cleaner

Hello everyone,
I have a child with psoriasis and their specialist has advised we switch our laundry powder/detergent to one without chemicals.
I had a look at the supermarket choices and they are very expensive.
I googled and apparently vinegar, baking soda or Epson salt can be used instead.
My question is has anyone made the switch to a natural alternative as stated above or otherwise that is cheap and does the same job as a detergent? What method do you use?
Thanks in advance 😊