I noticed it was tagged on GitHub on 4th March: https://github.com/mate-desktop/mate-desktop/releases/tag/v1.22.0
Read about the new features and fixes on the blog post here: https://mate-desktop.com/blog/2019-03-18-mate-1-22-released/
The various components of MATE Desktop 1.22 are available for download here: http://pub.mate-desktop.org/releases/1.22/