Hi!
Automatically performing the upgrade in the server would pretty much mean that downgrade is officially impossible.
Historically the server mostly worked fine without mysql_upgrade, with few exceptions (like, when a bug in collations required indexes to be rebuilt).
Supporting "downgrades" shouldn't be tied to whether or not a DBA ran mariadb-upgrade, but whether they upgraded a *minor* version or a *major* version. For minor version downgrades should be possible even after running mariadb-upgrade.
So you are implying now that if a user runs say MariaDB 10.6.9 and upgraded to 10.6.12 and ran mariadb-upgrade, and after a week of running 10.6.12 and some serious bug has occurred and the user wants to swap back to MariaDB 10.6.9 by going back to old binaries but still keep running oldest data it is no longer possible in MariaDB?
If the above is no longer possible in MariaDB, how long do you recommend users to run a new binary but postpone running mariadb-upgrade after upgrading to a new minor version? A week? A month?