In my desktop (105 keys HP keyboard) the "super" keys are indicated as:
Mod4+Super+Hyper or Super or Super L or Super R
depending the key combination, pressing sequence and setting menu used!
(pressing Ctrl before the super key has different output than pressing super key and then Ctrl).
From "System Settings, Keyboard, Shortcuts, Typing, Switch to ... source:", I managed to control various keyboard layouts using Ctrl+Menu and Alt+Menu
As the final release is almost here, I feel we cannot specify a bug now, so my work around is:
(for Lubuntu replace "gedit" with "leafpad")
sudo gedit /etc/default/keyboard
Change parameters to appropriate (below is the example for Us/Gr):
Save edited file, log-out, log-in and test it (possibly you have to reboot).
When you have just 2x layouts you can use "scroll LED" for the indicator:
Above worked on an installation. Using LiveCD/LiveUSB cannot reboot or logout, so use the terminal command:
(2x layouts toggle with Ctrl+Shift and scroll LED as the indicator)
setxkbmap -option grp:ctrl_shift_toggle,grp_led:scroll us,gr