OpenShift docs instruct users to download Butane and coreos-installer binaries from their latest directories on mirror.openshift.com.  The mirror does distribute previous versions of the tools, but only has one latest directory per tool, so users on all OCP versions will use the latest binaries.  So far that hasn't been a problem, since both Butane and coreos-installer provide backward compatibility with older RHCOS versions.

However, OCP 4.13+ is based on RHEL 9.  We're currently still shipping RHEL 8 tool builds on the mirror, but we aren't otherwise maintaining RHCOS on RHEL 8, so it would be nice to switch to RHEL 9 builds.  However, programs compiled against RHEL 9 libc won't run on RHEL 8, and coreos-installer compiled for RHEL 8 won't run on RHEL 9 without the compat-openssl11 package installed.

Determine how long to continue shipping RHEL 8 binaries on the mirror, whether to have a transition period where we ship both 8 and 9 binaries, what the directory layout for the latter would look like, and how we can communicate the change to users.

When we execute on these decisions, we'll need user-facing docs (since none of the options are transparent to the user), plus documentation in our own release checklists to prevent confusion.