As of today all Chef owned community cookbooks now require at a minimum Chef 12.1. All cookbooks have been released, and major version numbers have been bumped to follow SemVer. If you’re not yet on Chef 12.1 or later you can pin you cookbooks to the current major version you’re running to retain Chef 11 support.
Dropping support for Chef 11 in Chef owned community cookbooks allows us to use new features such as multi-package installation, new ohai plugin data, and most importantly Custom Resources. This will allow us to write better cookbooks for the community. It also brings our testing in line with our supported Chef releases since we test all contributions on Chef 12.
-Tim