The RPM given on the official website does not have the pgadmin4 package for Fedora 30.
Is there a known workaround?
Edit: Relevant packages are now included in the RPM, so there is no issue anymore.
You'd have to wait until Devrim gets around to rolling RPMs for Fedora 30.
The alternative is to build the software from source.
EDIT: In the meantime, packages for Fedora 30 are available.