FYI the CH trainer (September 20, 2017) for latest WRC 7 v1.4 still works.
Only yesterday did I find out that the trainer actually worked for v1.2, since the game version before that (i.e. the one I downloaded during the Steam Xmas Sale did not). Today the game was updated again to v1.4 now. And luckily as I just tested, everything still works.
I mention this because I find the whole matter totally strange, since normally any change i.e. update in a game's .exe also breaks the trainer. And normally a non-working trainer never works from then on. Whatever the CH folks are doing to keep things working... thanks.
Fortunately the latest game update was only about audio and visuals and didn't affect any game mechanics.