This, give-away HAS EXPIRED however here's some info on using the LEAPP utility to go from RHEL 7.x to 8.x. NOTE: Please see the documentation link here and the link 2 paragraphs down. Migration from RHEL 6 requires more steps

Please always use the latest edition of RHEL 8!
The latest edition is RHEL 8.5 as I type this in July of 2021.

This article here https://access.redhat.com/articles/4263361 says to use the most current edition of Red Hat Linux which is version 8.5 as I type this on July 20th, 2021. Using a non-current edition of Red Hat Linux 8 is not supported (see the link in this paragraph for specifics).

    IMPORTANT:
    A path for an automated in-place upgrade is going to be provided only for the latest even number RHEL 8 minor version, for example RHEL 8.5.

The procedure of upgrading from RHEL 7 to RHEL 8 using the Leapp utility is documented in Upgrading from RHEL 7 to RHEL 8. Major differences between RHEL 7 and RHEL 8 are documented in Considerations in adopting RHEL 8.

Do you have a backup of your important data? Please make one prior to upgrade! It is good to have a backup plan.

Consider cloning your system using "P to V" (physical to virtual) first if possible to evaluate the process if you want to reduce risk. Things like VMware offer "P to V".

Kind Regards,
RJ