+++ distrib/miniroot/install.sub
@@ -1807,6 +1807,10 @@ install_files() {
                rm -rf /mnt/var/syspatch/*
        fi

+       # Transition font cache ownership from root to its dedicated user.
+       # XXX Remove after 7.9 release.
+       chown -R _fc-cache:_fc-cache /mnt/var/cache/fontconfig
+
        # Install the set files.
        for _f in $_get_sets; do
                reset_watchdog

I don't think this can be removed for a long time, because sysupgrade
-R allows for quite arbitrary jumps between release builds.