SNCF has finally linked the youth discount card to the regular traveller's loyalty program, and made everything available on the mobile app…a month before I leave.
The physical discount card is literally a piece of heavy paper the size of an airport boarding pass. They even give you a little case for it with a built-in holder for the regular loyalty card, which is a normal-sized card with a QR code printed on it.
I don't see why this wasn't done in the first place. How hard is it to design something properly before launching it? Such incompetence.