One down, five to go.
Nintendo UK has released a launch trailer for the first wave of the Booster Course Pass for Mario Kart 8 Deluxe. You can now buy the Booster Course Pass on the Nintendo Store, which includes all 6 waves, each wave includes 8 courses, and all of them will be released by the end of 2023. If you already own Nintendo Switch Online + Expansion Pack, then you can hop in the new courses now with no additional cost.
You can check the full races of the first wave here, shortcuts, tips, and tricks here, and the graphic comparisons to the original courses here. If you’re eager to know what courses future waves might contain, then this datamine leak might give you a hint.