I have noticed that allaboard.eu is now also selling interrail reservation for france and maybe other countries, and they only charge a 1€ fee compared to the 2€ fee of other places like the interrail reservation service or raileurope.com. But it seeems like they do not sell reservataion for Ouigo trains, they dont even appear in their planner.
They also sell reservation for other countries (but for most of the other ones they sell it is possible to book reservations online directly from the operator)
Anyone already tried them out for reservations? (I know they have been selling passes for a while, is them selling reservations a new thing?)