I have had the same issue for the past few months, the shortcut that I use (Win+Space) to switch between the different keyboard layout is disabled every time I reboot my computer. Another issue is that on the lockscreen, I don’t have the option anymore to change the keyboard layout (so if I leave my computer, and it goes to sleep after a while, and the keyboard layout was left on Russian or Mandarin, I can’t log back in!). I’m on the latest Opensuse Tumbleweed with KDE. Thanks a lot.
actually the predefined switch has no shortcut initially if I remember correctly. The good news with the latest update is that the language switch is again available on the login screen.