Hint for migration from CentOS Stream 9 to Alma 9

In the generally good recipe given in
Migration - Linux @ CERN
there is one step missing, leading to an error that made me very nervous because it was not mentioned in the troubleshooting:
If you have the AFS client running, you should stop it with
/bin/systemctl stop openafs-client.service
before executing the step
dnf distro-sync --allowerasing --disablerepo=openafs*
Among many other things, this command will try to reinstall filesystem-3.16-2.el9.x86_64.rpm, which will fail with
error: unpacking of archive failed on file /afs: cpio: chmod failed - Device or resource busy
and at the end
Error: Transaction failed
which made me almost freak out, fearing that the system was now messed up.
But after stopping the afs client, the distro-sync completed cleanly, and the subsequent reboot into the new Alma9 was successful.