Groetg Frost From the comment section of that video:
Example - AuroraStore
Append "/-/tags?format=atom" to the end of the URL
RSS Feed URL: gitlab.com/AuroraOSS/AuroraStore/-/tags?format=atom
With AuroraStore when I downloaded the APK from GitLab I noticed it ended in ".zip". Using your file manager on your device, rename the file and remove the ".zip" so it ends in ".apk". There's no need to extract the file, renaming it allows you to install it like a standard APK.
For context for everybody else, here's the video we're talking about: