What does the double USB u shape male attached to the ribbon cable on the pi-top do?
It looks like its to power the Pi but then why does it need two USB for that? Is the 2nd one for data?
Why didn’t they just use the GPIO bridge for this?
Those that have moved/removed this cable how did you do it? To mount a Pi 4 or 5
The stacked USB ports at the back connect via the hub / bridge to:
Pi-top Keyboard
Touchpad
USB 2.0 port on top of Pi-Top bridge
BOTH of those USB ports must be connected! Be careful, some Pi Zero to 3b adapters and SBCs have only 1 USB port in that location.
Check that adapter or SBC has both ports.
Also check carefully as on some SBCs the lower left USB port may be only for flashing firmware, this is rare but there are so many SBC options its worth checking first.
Pi-top provides power via the 40 pin connector only. the GPIO pins are mirrored to the expansion connector on the right edge of the Pi-top hub board. Without that bridge on the 40 pin GPIO there’s no way to power the SBC but also the battery level is monitored via GPIO as well.