aimeos The PHP e-commerce & shop framework

https://aimeos.org/
not many extensions so far

Laravel eCommerce An Opensource eCommerce platform for all to build and scale your business.

https://bagisto.com/en/
We'll see if it gains an ecosystem

Vanilo is an E-commerce framework for Laravel

https://vanilo.io/
we'll see if it has legs

Sell downloads and tangibles!

https://www.e-junkie.com/
another entry-level ecommerce solution

LiteCart is a free e-commerce platform developed in PHP.

https://www.litecart.net/
Another PHP-based shopping cart program. Probably worth a try. 

AvoRed A Laravel Open Source Shopping Cart

https://www.avored.com/
An e-commerce shopping cart based on Laravel. We'll see if they grow an ecosystem.

LiteCart is a free e-commerce platform developed in PHP.

https://www.litecart.net/
Another ecommerce platform. We'll see if it gains any traction.

snipcart shopping cart platform for any website

https://snipcart.com/

A hosted shopping cart that can be added to any website, kinda like ecwid, I guess. Cost: 2%