There is no one-size-fits-all answer to this question, as the best e-commerce platform for a business-to-business (B2B) company depends on the specific needs and requirements of that organization. However, some popular open source e-commerce platforms that may be worth considering include Magento, PrestaShop, and WooCommerce.
When choosing an e-commerce platform, it is important to consider factors such as the size and scope of your business, your budget, and the level of customization and support you require. You may also want to look into platform-specific features, such as whether the platform offers B2B functionality out of the box or if it can be added through extensions or plugins.
Ultimately, the best way to determine which e-commerce platform is right for your B2B company is to consult with an experienced e-commerce development team who can assess your specific needs and recommend a solution that will fit those requirements.