Magnolia 5.6 reached end of life on June 25, 2020. This branch is no longer supported, see End-of-life policy.
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Using activation is still possible, but only after replacing the Publishing module and the Publishing Transactional module with the Activation module and the Transactional Activation module, respectively. You can do this in two ways:
../WEB-INF/lib
folders of your author and public instances. Add the activation JAR files in their place.