Morning,
I'm seeing an issue with the OL8 EPEL Repo, where the RHC package has been added to the core group in the comps.xml file, however this package is not included in the EPEL repo, and so far as i'm aware it's not supposed to be in here as per the 8.4 release notes, https://docs.oracle.com/en/operating-systems/oracle-linux/8/relnotes8.4/ol8-PackageChangesfromtheUpstreamRelease.html
This can be tested for with dnf install @core
after adding the epel repo, I am assuming that the epel repo should not have a core group at all.
See: https://yum.oracle.com/repo/OracleLinux/OL8/developer/EPEL/x86_64/repodata/a28d4cdaedc2f2b2d26d86fe24723494622c50c6ed7bd3b14bca095af074900c-comps.xml
<group>
<id>core</id>
<name>core</name>
<description/>
<default>false</default>
<uservisible>false</uservisible>
<packagelist>
<packagereq type="default">rhc</packagereq>
</packagelist>
</group>