An installer for JDK from AdoptOpenJDK would be a welcoming addition.
The Oracle OpenJDK 11 LTS builds will only receive updates for 6 months, while AdoptOpenJDK will commit to providing builds until LTS EOL.
OpenJDK provides a new feature release every six months, and a maintenance/security update based upon each active release every three months. We will follow this schedule for publishing binary releases from AdoptOpenJDK to ensure you get the latest, most secure builds.
In addition, every three years one feature release will be designated as the Long Term Supported (LTS) release. We will produce LTS releases for at least four years. This assurance will allow you to stay on a well-defined code stream, and give you time to migrate to the next, new, stable, LTS release when it becomes available.
Though we still need the Oracle JDK Installer, for those who still use an older JDK.
We have some legacy application using JDK 1.6 and JDK 1.7.
I like Baptiste Mathus suggestion of Using a repository manager like Nexus to get the JDK. Then you could get the JDK from your preferred source.