The Switcher Studio app has options for both English and for French. The language that appears depends on which language your iPad or iPhone has listed as the higher preference.
To check this, open the grey Settings app:
Settings => General => Language & Region => Preferred Language Order
If English is listed above French, then the Switcher Studio app will show in English.
If English is listed below French, then the Switcher Studio app will show in French.
**NOTE: No other languages are available at this time!!**