Hi!
Issue is still present on sid:
||/ Name Version Architecture Description
+++-==============-============-============-=================================
ii sddm 0.18.1-1 amd64 modern display manager for X11
With following /etc/default/keyboard contents on sddm greeter I can see
and choose only "us" layout.
% cat /etc/default/keyboard
# KEYBOARD CONFIGURATION FILE
# Consult the keyboard(5) manual page.
XKBMODEL="pc105"
XKBLAYOUT="us,lv"
XKBVARIANT=",apostrophe"
XKBOPTIONS="ctrl:nocaps,grp:shift_toggle"
BACKSPACE="guess"
% localectl
System Locale: LANG=en_GB.UTF-8
LANGUAGE=en_GB:en
VC Keymap: us
X11 Layout: us,lv
X11 Model: pc105
X11 Variant: ,apostrophe
X11 Options: ctrl:nocaps,grp:shift_toggle
Keyboard layouts work as expected when logged into Plasma session.
One interesting detail is that when I run sddm-greeter in test mode from
signed in session I can see that both layouts are available in keyboard
layout drop-down.
% sddm-greeter --test-mode
BR, Juris