I downloaded and installed the Windows x86_64 OSATE 2.6.0-vfinal release of OSATE from osate.org.
I extracted it and checked Help -> About -> Plugins and saw xtext 2.19 installed.

I did help -> install new software -> and added an update site: https://osate-build.sei.cmu.edu/download/osate/stable/2.6.0-vfinal/updates/
I selected the available features and clicked "install"
After the install completed and I restarted OSATE, Help -> About -> Plugins reported most xtext plugins were now at version 2.20.
This breaks some of our tools, because we have dependencies on xtext 2.19.

I downloaded and installed the Windows x86_64 OSATE 2.6.0-vfinal release of OSATE from osate.org.
I extracted it and checked Help -> About -> Plugins and saw xtext 2.19 installed.
I did help -> install new software -> and added an update site: https://osate-build.sei.cmu.edu/download/osate/stable/2.6.0-vfinal/updates/
I selected the available features and clicked "install"
After the install completed and I restarted OSATE, Help -> About -> Plugins reported most xtext plugins were now at version 2.20.
This breaks some of our tools, because we have dependencies on xtext 2.19.