I installed under 9.0 normal with Trackmania United. Then i downloaded and installed the Forever Upgrade Patch.
I only get a white screen after starting, but with alt + enter you can switch to window mode.
With 9.0 i managed to use the menu, but with loading a track it crashed.
Now with 9.1 the same trick with window mode is working and some time i managed to get it working in full screen aswell.
I also played through a whole track, but after that it crashed. Every here and then it crashes with a runtime error even in the menu or at loading the track.
So it is still far away from being playable, but it works better than in 9.0.