- I disabled "Keep system layouts" in settings.
- Added my secondary language (Arabic) to keyboard layouts.
- Modified the layout change keys to: "Alt+Shift" and "Left Alt+Left Shift".
My (right) "Alt+Shift" keys successfully change the language from English to Arabic but never back! Left Alt+Left Shift are working just fine.
Being right-handed I really need to get the right Alt+Shift keys to successfully swap between the two input languages.
OS: Lubuntu 18.04 x64 - I clean-installed it today.