Change language layout in screen lock

I'm running Ubuntu 21.04 and the "dbus-monitor" solution didn't work for me, So I'm sharing the way I approached it.
using xscreensaver-command we can monitor status changes of the screensaver.
Then when the status change to LOCK, we can change the layout to us and change it back once the screensaver "release" the desktop

Once I had the script, I set it to run during login.

xscreensaver-command --watch | 
  while read MSG; do
    CMD=`echo $MSG | awk '{print $1}'`
    if [[ "$CMD" == "LOCK" ]]; then
        ##### CURRENTL=$(setxkbmap -query | grep layout | awk '{print $2}')
        echo "Locked with current layout ${CURRENTL}"
        setxkbmap us
    fi

    if [[ "$CMD" == "UNBLANK" ]]; then
        ##### setxkbmap $CURRENTL
        setxkbmap us,il,us
        echo -n "Returning to "
        setxkbmap -query | grep layout | awk '{ print $2 }'
    fi
    # echo $CMD
  done

I just improved the previous examples for Ubuntu 20.04

dbus-monitor --session "type=signal,interface=org.gnome.ScreenSaver" | 
  while read MSG; do
    LOCK_STAT=`echo $MSG | grep boolean | awk '{print $2}'`
    if [[ "$LOCK_STAT" == "true" ]]; then
        CURRENTL=$(setxkbmap -query | grep layout | awk '{print $2}')
        echo "Locked with current layout ${CURRENTL}"
        setxkbmap us
    fi

    if [[ "$LOCK_STAT" == "false" ]]; then
        setxkbmap $CURRENTL
        echo -n "Returning to "
        setxkbmap -query | grep layout | awk '{ print $2 }'
    fi
  done

xscreensaver is great but the maintainer, JWZ, has made clear that he has no intention of supporting multiple keyboards.

xsecurelock is a better solution. It supports switch keyboard layouts from within the screen saver and will also give you a bold red notice if caps lock is on. It doesn't have a built-in timer like xscreensaver does so you'll need to follow the instructions on their webpage to get it to run automatically after a timeout.

Ubuntu 16.04 use another interface name:

dbus-monitor --session "type=signal,interface=com.canonical.Unity.Session" | 
  while read MSG; do
    LOCK_STAT=`echo $MSG | egrep -o member='.*' | cut -d '=' -f 2`
    if [[ "$LOCK_STAT" == "Locked" ]]; then
        CURRENTL=$(setxkbmap -query | grep layout | awk '{print $2}')
        echo "Locked with current layout ${CURRENTL}"
        setxkbmap us
    fi
    if [[ "$LOCK_STAT" == "Unlocked" ]]; then
        setxkbmap $CURRENTL
        echo -n "Returning to"
        setxkbmap -query | grep layout
    fi
  done

[Edit] This might be a workaround but right now its messing with other layout switching keybindings

[Original] This one worked for me BUT I couldn't run it on startup and keep it running in background.

Listen to lock signal and change layout to the one of your password. (ugly workaround but seem to work)

dbus-monitor --session "type=signal,interface=org.gnome.ScreenSaver" | 
  while read MSG; do
    LOCK_STAT=`echo $MSG | grep boolean | awk '{print $2}'`
    if [[ "$LOCK_STAT" == "true" ]]; then
        setxkbmap us
    else
        setxkbmap -option grp:switch,grp:alt_shift_toggle,grp_led:scroll us,il
    fi
  done

I have the exact same problem as you and I get around by doing this:

• get rid of gnome-screensaver by:

  sudo apt-get purge gnome-screensaver
  

• Install the X screensaver by:

  sudo apt-get install xscreensaver xscreensaver-data xscreensaver-gl
  

Whenever you forgot to switch back to English before the system locks itself, hit Ctrl+Alt+F1 log in as your admin user and kill -9 xscreensaver and you're back in!

(It's just a workaround and not a real "solution" but it works for me and is definitely better then shutting down and restarting)