FCL.055 Language proficiency Regulation (EU) 2020/359
(a) General. Aeroplane, helicopter, powered-lift and airship pilots required to use the radio
telephone shall not exercise the privileges of their licences and ratings unless they have a
language proficiency endorsement on their licence in either English or the language used for
radio communications involved in the flight.
That's what it says... I only ever have had a LPE in English on my licence, so don't know how this works in other countries where RT may be conducted in other languages.
From:
https://www.easa.europa.eu/en/easy-a...ncing-part-fcl