Images are hosted on Github Container Registry here.
We host a dedicated mirror repostiory, these containers are mostly copies from official trusted sources.
This is to get around Docker Hub rate-limiting (100 pulls / 6 hours, or authenticated 200 pulls / 6 hours). It is considered a stop-gap until the maintainers of the applications below support a different Container Registry.
We also sometimes need to apply small patches and additions for our users: For example, adding nano and extra-packages to Nextcloud