COPPER 5.1 has just been released and is ready for Java 13. It is available on GitHub and in Maven Central.
COPPER has been upgraded to ASM 7.2, so Java 12 and 13 are now supported.
COPPER 5.1 adds support for git as workflow repository in order to enable a lightweight CI/CD pipeline using git repositories for changes in workflows. (Changes outside the workflows are not in scope of this pipeline.)
However, if you don’t need this feature, you can use COPPER the same way as before.