https://www.itzgeek.com/how-tos/linux/centos-how-tos/how-to-upgrade-from-rhel-7-to-rhel-8.html
To určitě funguje na RHEL. Jestli je to součástí CentOSu nevím.
rhel-7-server-extras-rpms contains leapp for upgrade CentOS 7 to 8. Will CentOS extras provide leapp?
There are no plans for the CentOS core team to support or package leapp but if there is sufficient support from the community to provide copies amended for CentOS then they could be released as part of a SIG. However, given the current lack of support for the preupgrade tool to migrate from CentOS 6 to 7 and the total lack of response to all calls for volunteers to package that, I would not be optimistic about it happening.