Our default installation path for Tumbleweed in the ARM world is to append
"usessh=1 sshpassword=xxx network=1" to the installer command line.

That way we can install systems easily from remote.

With the recent changes in sshd that disallow root by default, we can no longer
ssh into the installer system as root. So we can not install.

To keep in mind as a follow-up on this; if we did manage to ssh in and install,
but did not select a default user to get created (which is my usual
installation option, why bother with non-root for starters?), we would get
locked out of the real system after installation.

So the fix for this IMHO would be to modify sshd_config to allow root access in
instsys and then ensure that if this is the mode of operation, that same config
propagates into the installed system.