SWF discovered a new tech that allows you to infinitely use your second jump over ground, much like Bowser’s infinite sideB jump.
The thread linked goes into more detail, but basically here’s the deal:
If you use an attack that ends it’s animation slightly before you hit the ground, you can buffer a jump out of it. If you time it precisely (the timing differs from character to character because of jump heights and moves) you should jump just as you land. The game seemingly registers you both as on the ground and aerial at the same time, so you jump from the ground using your second jump instead of getting landing lag.
Now, this is obviously more useful to some characters and not so much for others. Characters with heavy landing lag (Bowser, DK, Ganon, etc.) seem to benefit more, as they can cancel out landing lag. For faster characters it doesn’t matter so much as their lag is already nonexistent. Overall, not anything close to a gamebreaking tech, but it may prove to be somewhat useful.