https://docs.redhat.com/en/documentation/red_hat_jboss_enterprise_application_platform/8.0/html-single/migration_guide/index#preparing-for-migration-to-jboss-eap-8_default

Chapter 2.0

"JBoss EAP 8.0 provides backward compatibility for JBoss EAP 7 applications. However, if your application uses features that JBoss EAP 8.0 has deprecated or removed, you might need to modify your application code. "

This paragraph is completely wrong and needs to be removed.

EAP 8 provides NO backwards compatibility with EAP 7 applications whatsoever.

EVERY real world application must be modified to work in EAP 8 due to major breaking changes (notably javax->jakarta renaming).