Can the prayer times from the the Union of Islamic Organizations of France (UOIF) application in France be relied upon, given that there are differences between internet applications?

If it is not possible to ascertain the beginning of the prayer time by the شرعية ( Shar’i ) signs, and the calendars differ, then act according to the calendar approved by trustworthy scholars. If such a calendar is not available, or if there is more than one such calendar, then act according to the latest entry time for the prayer.