Comment # 2 on bug 1209594 from Stefan Dirsch

keytable only takes care of $KEYMAP $KEYMAP_TOGGLE variables in
/etc/vconsole.conf. This is what YaST uses during installation.

  localectl set-keymap $KEYMAP $KEYMAP_TOGGLE

(KEYMAP_TOGGLE is a second keymap)

Some history

rpm --changelog -q xdm

[...]

* Wed Oct 18 2017 sndirsch@suse.com
- reintroduced /etc/X11/xdm/keytable script and the hook-up in
  /usr/lib/X11/display-manager to setup X11 keymaps, since YaST
  is not able to use localectl already during installation due to
  dbus and appropriate systemd services not running :-(
  (bsc#1046436)

[...]

* Mon Feb 06 2017 sndirsch@suse.com
- no longer try to configure Linux console and X11 keymaps
  according to setting in /etc/vconsole.conf; this needs to be done
  via localectl by YaST itself now; /etc/X11/xdm/keytable removed
  and no longer invoked by /usr/lib/X11/display-manager (bnc#1023211)

[...]

* Thu Jan 29 2015 sndirsch@suse.com
- /etc/X11/xdm/keytable"
  * improved warning message, when mapping for console keyboard
    doesn't exist (bnc#914880)


I don't see why this would be a new issue for you, which came with a systemd
update.