Are there Docker Hub comparable public Docker image repositories? Historically, you can download official community software from a distributed mirror network.

Even for Java Maven, there are two sites globally.

But what is about Docker Hub? What if Docker, Inc. decides to close the Hub or the site will become unstable?

Beyond just having business critical images which you can rebuild and store locally, Docker Hub is also:


indicator that a release is official
often provides Dockerfile which is very valuable configuration knowledge
provides links to backing GitHub projects
features like starring and download numbers


Are there other mirrors not hosted by Docker either comparable initiatives so that an open source community would say "ok we can publish our release also there"?

After a short research, I see there are many products to setup your own registry, but not an alternative Hub site.
With Docker following the Open Container Initiative, in the event that Docker were to disappear, people would still have access to images stored outside of Docker Hub.

While there is not a public mirror of Docker Hub, you do have access to other registries that often store the official image.

For example, if you were to pull the official Docker SQL Server image, you would target mcr.microsoft.com/mssql/server:2019.  So even though the image can be searched on in Docker Hub, the image still exists outside of Docker Hub.  The three big cloud providers (Azure, AWS, and Google) all have container registries that allow public access.  Many of the cloud registries support storing of images in regions and would allow "mirrored" architectures that are transparent to the public and disaster recovery (i.e. end users only pull from one link and the provider routes to an active available registry).