As you can see from the first image, there are a couple of small-ish details that have changed. The cockpit mounted vortex generators that sat just behind the rear view mirrors are gone, there are now slots in the floor, and yes these are legal, they run all the way to the edge of the floor. The vertical fence that the slots connect to actually have a cut-out in them that allows a small amount of exhaust gas flow to enter the slot. It’s a very small amount, but it increases the effectiveness of the slot.
There’s also some small changes to the front wing, the inner most edges are smaller in width, but larger in height, creating a much stronger vortex. Also the ‘endplateless’ design is now split into 4 sections. The R-shaped cascade element is now gone, its use was to create a vortex that went over the top of the front wing upper element, but as that now generates its own much stronger vortex, it was no longer needed and just created extra drag.
Also there is a new front suspension design. Slightly stronger mounts at the wheel, and front chassis mount. It’s designed in such a way that if it broke off in a head-on collision, the rear mount would fail first, and the suspension elements would travel outboard rather than inboard as it would’ve done in the previous design. This means safer accidents for the drivers.