Too many changes to count, but the important ones are Create v6, Create Simulated (+Aeronautics+Offroad), and 1.21.1 Neo. The pack is also much lighter, but some of it is due to bugs and incompatibilities that need to be fixed first with certain mods.
I also have to update my own mods as well, and reconfigure everything (I restarted configs from scratch).
This is pretty early, don't expect anything polished, but at least you have a somewhat decent pack you can use to play Aeronautics with your friends!