Sylius is described as 'Open Source eCommerce Platform on Symfony' and is a E-commerce System in the Business & Commerce category. There are more than 50 alternatives to Sylius for a variety of platforms, including Online / Web-based, Self-Hosted solutions, Linux, SaaS and PHP. The best alternative is ISPmanager. It's not free, so if you're looking for a free alternative, you could try WooCommerce or PrestaShop. Other great apps like Sylius are Thirty Bees (Free, Open Source), OpenCart (Free, Open Source), Adobe Commerce (Free Personal, Open Source) and Shopify (Paid).
thirty bees is an open source e-commerce software that empowers merchants to focus less on their shop and more on their business. Having a fast, responsive, bug free e-commerce site is essential now, and thirty bees fills that void.
OpenCart is an open source PHP-based online shopping cart system. A robust e-commerce solution for Internet merchants with the ability to create their own online business and participate in e-commerce at a minimal cost.
Arastta is the next generation of eCommerce software built with modern technologies such as Symfony, MVC, Bootstrap, jQuery, Swift Mailer etc. Thanks to it's modular and lightweight structure, Arastta provides an awesome marketplace for theme and extension developers.