Vue Storefront - Open Source PWA for any eCommerce
MarketplaceKit - MarketplaceKit is a platform for building different types of online marketplaces.
Square Online Checkout - Create easy pay links for whatever you're selling and start accepting payments everywhere online.
JaJuMa-Market - All-In-One Multi-Vendor / Online Marketplace Solution. Various Business Models supported.
Shopify - Shopify is a powerful ecommerce platform that includes everything you need to create an online store and sell online. Try it free for 14 days.
Sharetribe - Build your online marketplace business. You don't need a developer.