I heard that, because the developer of this game drove the ATs while playing with different physics, some ATs are now impossible, but I couldn't find out which ones. Does anyone know which are affected?

I know that info comes from a trackmania iceberg video, but the video doesn't have any sources or info backing up that statement. I do not think there is anything to support the idea that the developers played on different physics. All the TrackMania DS ATs are even listed online, here: https://web.archive.org/web/20210422201042/https://en.tm-ladder.com/time_page/index.php?game=ds All of them are possible to get.

And like rphd mentioned, there is one instance of an impossible AT in TrackMania Turbo: Build to Race (DS). The impossible track is CoastC5, and you can see a video about the details here: