Here is a link to the documentation: DNF5 Package Management Utility — dnf5 documentation
It says: Correct operation of DNF5 depends on having an access to up-to-date data from the all enabled repositories, but contacting remote mirrors on every operation considerably slows it down and costs bandwidth for both the client and the repository provider. The metadata_expire repository configuration option is used by DNF5 to determine whether a particular local copy of repository data is due to be re-synced.
--refresh
does not seem to exist anymore.