If you're looking for something to replace AppManager, Kobble could be a good fit. Kobble is an all-purpose developer platform that can help you rapidly bootstrap SaaS apps with authentication, payments and email integration built in. It also has more advanced tools for user management, access control and quotas. The platform's no-code authentication portal and SDKs for integration with common frameworks make it easier to get to the monetization stage and start generating revenue.
Another option is ROQ. ROQ offers a data and API layer that makes it easier to build multi-tenant SaaS apps. It includes features like secure database queries, authentication, authorization and payments through Stripe integration. ROQ can help you build secure, scalable and resilient SaaS apps faster, which can help you get to market faster.
If you're interested in a no-code option, Softr offers a drag-and-drop interface to build custom client portals, internal tools and community hubs based on data in Airtable, Google Sheets and other sources. With features like fine-grained permission controls and integration with tools like Zapier, Mailchimp and Google Analytics, Softr is geared for teams of any size who want to build custom tools without programming skills.