It is impossible to use the rotate photo shortcut on a French keyboard since CTRL [ and CTRL ] cannot work.
The  keys are only available on a French keyboard with the ALT Gr key.
Thus CTRL ALTGr [ does nothing either.
I do not want to use the mouse to rotate 2000 photos.
Keyboard shortcuts vary from language to language. When LR's language is set to French, the shortcuts for rotate left and right are Shift+Cmd+; and Shift+Cmd: (Mac) / Shift+Ctrl+; and Shift+Ctrl+: (Windows), as you can see on the Library Photo menu:
Doing Aide > Raccourcis Du Module Bibliotheque will also show the most common shortcuts: