So I'm following the instructions at https://docs.oracle.com/en/database/oracle/oracle-database/21/xeinl/installing-oracle-database-xe.html for an EL8 system, and I get to this step:
# curl -o oracle-database-preinstall-21c-1.0-1.el8.x86_64.rpm https://yum.oracle.com/repo/OracleLinux/OL8/latest/x86_64/getPackage/oracle-database-preinstall-21c-1.0-1.el8.x86_64.rpm
# dnf -y localinstall oracle-database-preinstall-21c-1.0-1.el8.x86_64.rpm
and every time I run the command, I get a .rpm file, but the contents of the file say 'Not Found', and so obviously the operation fails. I've run this originally from an EL8 based system, and got the 'Not Found' file. I tried again from my Windows 10 workstation, and get miscellaneous errors and not found messages in my browser. I tried browsing the package repository, and couldn't find a package with the name 'oracle-database-preinstall', though because of the structure I can't just search by filename.