Note: FRA Mandatory Minimum Kit (for Long A, Medium A and Long B races) comprises: waterproof whole body cover (with taped seams and integrated attached hood) + hat + gloves + map + compass + whistle + emergency food. Maps must be on paper. Compass must be conventional non-electronic type

If a runner chooses to use an electronic map, or has some photos on a phone to assist, I think it would be odd, but it seems permissible, so long as they have a paper map with them.