Assetto Corsa has, perhaps, the best mod community within all of sim racing.
Recently,
RaceDepartment achieved 10,000 uploads for AC with content ranging from new cars, tracks, telemetry tools, graphical/shader changes, FFB tweaks, etc, etc....
If anyone wants to try sim racing, Assetto Corsa is the title to try! And it will live on for another 5 years.