See the changes in configuration guide between EAP 7.4 and EAP 8.1:
https://gitlab.cee.redhat.com/red-hat-jboss-enterprise-application-platform-documentation/eap8-documentation/-/merge_requests/462

All these changes needs to be covered in server migration tool, for example:

"/subsystem=remoting/configuration=endpoint" confuguration is not availble anymore