milhouse I will wait for the USB booting then. I was wondering if I can use the following method (I guess it should be faster):
- Download RPi4 image and manually upgrade my RPi3 with it (update folder).
- After rebooting my RPi3 should show the rainbow screen (firmware not right)
- Activate USB boot on my RPi4 (when available)
- Plug in my USB HDD in the RPi4 and cross fingers
What do you think?