Known Limitations

Activity Diagram

Sequence Diagram

Eclipse environment with org.eclipse.uml2

Both solutions are registering to EMF their own implementation for handling .uml and .uml2 file extensions.
For avoiding conflicts, registration of com.sodius.mdw.metamodel.uml21 can be disabled by adding an environment variable:
com.sodius.mdw.metamodel.uml21.enableRegisterResourceFactories to "false"

This environment variable could be set inside eclipse.ini of the running product, after -vmargs field:

This would make org.eclipse.uml2 as default reader for .uml and .uml2 files.