From my article "How to Avoid Funding the American Deep State":

'In addition to all the closed-source alternatives there are to Amazon, eBay, Alibaba, etc., there's OpenBazaar. It's open source and peer-to-peer, and there are no fees. You can only pay with cryptocurrencies though.

There's also BriskSale.

"We have been considering making BriskSale open-source. There’s a chance we will in the future, but for now it’s private." - Ryan Speier, founder of BriskSale

BriskSale doesn't charge sellers listing or sales fees. You can offer a commission though, in which case BriskSale and BriskSellers will race to find a buyer. But, at the moment, there's a catch:

"To ensure maximum visibility, every item listed on BriskSale is automatically uploaded to the Google Shopping network."

BriskSale pays Google for that, so: https://www.brisksale.com/contact-us'