The menu language on reMarkable is English.
The handwriting conversion feature currently supports the following languages:
Basque, Bulgarian, Catalan , Croatian, Czech, Danish, Dutch, English (Canada), English (United Kindom), English (United States), Estonia, Finnish, French (Canada), French (France), Galician, German (Austria),German (Germany), Greek, Hungarian, Icelandic, Irish, Italian, Latvian, Lithuanian, Norwegian, Polish, Portuguese, Romanian, Slovak, Slovenia, Spanish and Swedish.
Available keyboard languages are American English and norsk bokmål. Select your keyboard language in Keyboard settings.