Google Tag Manager vs Rudderstack: What are the differences?
Google Tag Manager: Quickly and easily update tags and code snippets on your website or mobile app. Tag Manager gives you the ability to add and update your own tags for conversion tracking, site analytics, remarketing, and more. There are nearly endless ways to track user behavior across your sites and apps, and the intuitive design lets you change tags whenever you want; Rudderstack: An open source alternative to segment. It is a platform for collecting, storing and routing customer event data to dozens of tools. It is open-source, can run in your cloud environment (AWS, GCP, Azure or even your data-centre) and provides a powerful transformation framework to process your event data on the fly.
Google Tag Manager and Rudderstack can be categorized as "Analytics Integrator" tools.
Rudderstack is an open source tool with 1.58K GitHub stars and 59 GitHub forks. Here's a link to Rudderstack's open source repository on GitHub.