Support for the December 2019 releases of Melodic, Crystal, Dashing, and Eloquent has been added to the [thud-draft] and [build-draft] branches of meta-ros and meta-ros-webos, completing Milestone 10.
A new revision 17 of the OpenEmbedded Build Instructions updated for this has been published. Its change log is here. A “rich diff” of the changes made since the previous revision is here.
This will be the last milestone with Crystal support because it has reached its EOL.