When I upgrade to Liferay EE6.1.20, by default there will start from a setup wizard, when I click Finish button, the error log shows: "com.liferay.portal.kernel.workflow.WorkflowException: No workflow handler found for com.liferay.portal.model.User". and I cannot by pass this page until I changed some code.
See in com.liferay.portal.workflow.WorkflowHandlerRegistryImpl.java the register(WorkflowHandler workflowHandler) method only accept WorkflowHandler type as its parameter, and the getWorkflowHandler(String className) method use a className String to retrieve the registered/cached WorkflowHandler, this seems ok.
but in com.liferay.portal.service.impl.UserLocalServiceImpl.java, while there invoke WorkflowHandlerRegistryUtil.startWorkflowInstance() method, there pass "User.class.getName()" as its className parameter, and in the WorkflowHandlerRegistryUtil.startWorkflowInstance() method, there will invoke getWorkflowHandler(className) to get the WorkflowHandler, so this will always throw a "No workflow handler found" WorkflowException. that's obvious, because there is no way to register a User class to the Map _workflowHandlerMap in WorkflowHandlerRegistryImpl.java.
I looked up the CE code on github, there also has such issue, I guess there should be "UserWorkflowHandler.class.getName()", not "User.class.getName()".