First of all, detergent pods are for dummies who cannot measure the right amount of detergent for a job and those who don’t know that water hardness is a factor. They are for convenience zombies who cannot be bothered to think. So from the very start, pods are not for solarpunks.
Someone told me they had a problem with their dishwasher because undisolved gelatin sacs were gumming up their drain. The linked article goes into clogs. This article (if you can get past the enshitification) says there is research on an environmental impact by pod sacks. So that’s also antithetical to solarpunkness.
So do it right. Fuck pods. They cost more anyway. Buy powdered detergent if you have soft water (or if your dishwasher has a built-in water softener) and use less (to avoid etching). If you have hard water, either use liquid detergent or just use a bigger dose of powder.
Most powdered detergents contain high amounts of salts which aren’t particularly good for anything downstream of your dishwasher.
I’m unsure of a salt-free dish detergent, but I can gleefully recommend Oasis Biocompatible Laundry Detergent for everyone, but especially anyone with a septic or greywater laundry system. It cleans great and breaks down naturally into plant food.
Some detergents say “septic safe” on the container. My folks bought the cheapest option which did not say one way or another, so I had to call the supplier, who then said it was septic safe. It’s a shame that in the 2020s we still don’t have transparency on what we buy.
“Septic safe” is a pretty loose definition, and usually means “this will not break anything” not “this will naturally break down into something that is not harmful to the ecosystem outside of your septic tank”, but it’s usually a good start