switch language with Option+Shift or Cmd+Shift

[pqrs-org]

switch language with Option+Shift or Cmd+Shift

[apm1467]

This can be indeed trivial. Just set the system shortcut of changing input source to be, for example, command + space. Then you can easily map option + shift to command + space with Karabiner-Elements. So every time you tap option + shift, the system will actually receive command + space and change the input source.

This can however break other shorts that uses the option + shift combination. You won't be able to use "Paste and match style" (shift + option + command + v) for example, since the system will receive command + space + v.

[bingocaller]

Do you mean the OS language or the keyboard layout/language?
The former is quite complicated because it would require running languagesetup, choosing a language, and restarting the system.
The latter can be set natively in your System Preferences.

[Thaina]

@bingocaller The latter

In macOS Option+Shift or Cmd+Shift cannot set as a keyboard language binding. It not activation key in macOS unlike in Windows

[bingocaller]

Ah, I didn't realise that! 🙂
Well, I guess it isn't going be trivial, then. You would probably have to set it up to do a shell_command (see caps_lock_enhancement.json for reference), which in turn cycles the keyboard layouts.
I did a bit of digging of how to do that programatically, and this Stack Overflow answer was the only thing I could find. It isn't exactly the most direct route, but might be what you're looking for or could at least help you on your way.