This code doen't work on Wayland for getting Capslock state.

caps_lock_state.py

#!/usr/bin/python3

import gi
gi.require_version('Gdk', '4.0')
gi.require_version('Gtk', '4.0')
from gi.repository import Gtk, Gdk, GLib, GObject


def on_keyboard_notify(keyboard, data):
    print(keyboard.get_caps_lock_state())


def main():
    display = Gdk.Display.get_default()
    seat = display.get_default_seat()
    keyboard = seat.get_keyboard()
    print(keyboard.get_caps_lock_state())
    keyboard.connect('notify::caps-lock-state', on_keyboard_notify)
    loop = GLib.MainLoop()
    loop.run()


if __name__ == "__main__":
    main()