USB 2 is possible, for some really dumb reasons. USB-IF actually prohibits repurposing the USB 2 pins for other purposes in USB 3.x capable connectors; effectively making it a separate bus from everything else. So you can route the USB2 pins on both C connectors to a hub chip and route everything else from the "privileged" port to the inner port. You will still need some kind of power mux so that the USB 2 port still gets power regardless of what port holds the power role.
This technically breaks the USB-IF rules[1] because you aren't supposed to disassociate the USB2 and 3.x pins like that. In practice as long as every device sees either just 2.0 or both 2.0 and 3.x pins, it's fine.
USB 3 onwards is a problem because of altmodes. The 3.x pins are officially referred to as "high-speed lanes" in the USB-C spec, because there's two of them and they don't have to carry USB 3.x. Every altmode[0] exclusively repurposes the high-speed lanes for some other kind of traffic. So USB 3 is effectively an altmode in and of itself. If you put a USB3 hub on those pins, then you lose altmodes, unless you have that magic hub silicon that doesn't exist that I mentioned in the parent comment.
[0] The USB2 lanes are forbidden to be reused by altmodes. Which is why VirtualLink is incredibly cursed.
[1] Yes I actually have mentioned this sort of thing in the Framework forums, no they won't actually sell a card like that. Consider it an EE exercise for curious Framework users.
