In Switchboard still can not install "Next Keyboard Layout" or "Previous Keyboard Layout" on the combination Shift+Ctrl/Shift+Alt. If this is done in the way of dconf "org → pantheon → desktop → gala → keybindings", then there is a conflict with other shortcuts.
For example if you set the layout switching on Ctrl+Shift, then stop working Ctrl+ Shift+T in the browser or Ctrl+Shift+V in the Pantheon Terminal, etc.
In Switchboard still can not install "Next Keyboard Layout" or "Previous Keyboard Layout" on the combination Shift+Ctrl/ Shift+Alt. If this is done in the way of dconf "org → pantheon → desktop → gala → keybindings", then there is a conflict with other shortcuts.
For example if you set the layout switching on Ctrl+Shift, then stop working Ctrl+ Shift+T in the browser or Ctrl+Shift+V in the Pantheon Terminal, etc.