Cannot create an additional database in Oracle 18c XE
Licensing Restrictions


  Oracle Database XE restricts itself to only one installation per
  logical environment. The logical environment can either be a virtual
  host such as a VM or container, or a physical host. If more than one
  Oracle Database XE installation is attempted to be started in such a
  logical environment, an "ORA-00442: Oracle Database Express Edition
  (XE) single instance violation error" is raised and the database will
  not start.