Any help is greatly appreciated (I'm already sick of trying to
understand what's going on here), thanks a lot in advance!

I have a problem with the standard for Xorg way of using multiple
keyboard layouts:

Section "InputDevice"
Identifier "Keyboard0"
Driver "kbd"
Option "XkbLayout" "us,ru"
Option "XkbOptions" "grp:shift_toggle,grp_led:caps"
EndSection

Without Option's, everything's OK, US keyboard works, of course. Adding
the two Option's leads to keys shifted one position to the left, i.e.
pressing 'y' yields 't', pressing 'g' yields 'f', etc. This happens
right away on the login screen, so it's not something specific to a
particular desktop environment, CDE or JDS.

This is snv_30 on Thinkpad X24.

$ locale
LANG=C
LC_CTYPE=C
LC_NUMERIC="C"
LC_TIME="C"
LC_COLLATE="C"
LC_MONETARY="C"
LC_MESSAGES="C"
LC_ALL=C

$ kbd -t
USB keyboard

$ eeprom kbd-type
kbd-type=US-English(104-Key)

Without InputDevice Option's, the Xorg log looks like this:

$ egrep -i 'keyb|xkb' /var/log/Xorg.0.log
(**) |-->Input Device "Keyboard0"
(II) Initializing built-in extension XKEYBOARD
(**) Option "CoreKeyboard"
(**) Keyboard0: Core Keyboard
(II) Keyboard0: Opened device "/dev/kbd"
(--) Keyboard0: Keyboard type: USB (6)
(--) Keyboard0: Keyboard layout: 33
(--) XKB: model: "sun_type6_usb"
(--) XKB: layout: "us"
(--) Keyboard0: XkbModel = sun_type6_usb
(--) Keyboard0: XkbLayout = us
(**) Option "XkbRules" "xorg"
(**) Keyboard0: XkbRules: "xorg"
(**) Option "XkbModel" "sun_type6_usb"
(**) Keyboard0: XkbModel: "sun_type6_usb"
(**) Option "XkbLayout" "us"
(**) Keyboard0: XkbLayout: "us"
(**) Keyboard0: CustomKeycodes disabled
(II) XINPUT: Adding extended input device "Keyboard0" (type: KEYBOARD)

--
/ynp