If you already have the language installed .. all you need to do is add the "Keyboard Layout Switcher" panel applet to the bottom panel.
Right-click the bottom panel, and select Add / Remove Panel Items
.. Click the + Add
button .. highlight the Keyboard Layout Switcher
and click the + Add
Now before you close the next window .. have a look at your bottom panel, the keyboard switcher will be there by your clock .. if you want to move it, use the Up
To use the Switcher .. just normal (left) click the icon on the panel and it should switch.
If it doesn't .. open a terminal (Ctrl+Alt+T), run this:
and post the contents of that file here.
I dunno if it will do the Alt+Shift keyboard shortcut .. but *maybe* we can add that keyboard shortcut later if you really want it.
OK, to add the Alt+Shift keyboard shortcut to toggle between Russian (ru) and UK English (gb) keyboards .. you need to add the line:-
@setxkbmap -option grp:alt_shift_toggle "gb,ru"
to the file:-
Then log off and on again (or reboot) for the changes to be applied.
Here's a single command to add that:
echo '@setxkbmap -option grp:alt_shift_toggle "gb,ru"' | sudo tee -a /etc/xdg/lxsession/Peppermint/autostart
now log off/on.
If you have the Keyboard Layout Switcher panel applet installed .. you'll also see the flag change.
Reference source (needs modifying as above for Peppermint):