I had the same problem, now it is solved.
- Go to your languages in settings.
- Click on the ... after any language.
- Choose language options
- Install keyboard, add the keyboard layout you want
This will fix both the language shift by keys AND the docking the languages in the taskbar.
After searching for the fix for several months, finally this worked for me. Thanks
PS. In Settings>Time & language >Language bar options > Language Bar, the "Docked in the taskbar" is greyed out. Since in Language Bar was set at "Floating On Desktop", once the language bar appeared following Endre's method, it floated on the desktop. Upon pressing Ctl_Space, all of a sudden the floating language bar was automatically docked to the task bar, even though the "Docked in the taskbar" is still greyed out.
Sorry, in the above post the Ctl_Space should be Start (i.e., Window icon)_Space. One might want to play around with Ctl_Space, Start_Space, and check/uncheck "Floating On Desktop" or "Hidden".