The BTT Pi manual BTT-Pi/BIGTREETECH Pi V1.2 User Manual.pdf at master · bigtreetech/BTT-Pi · GitHub says on page 11 to use the CB1 Armbian software Releases · bigtreetech/CB1 · GitHub. Did you use that software image?
First thing I would do is, get the OS running on the BTT Pi and then connect the printer.
I’m sure the BTT is good enough for Klipper, I wouldn’t waste your RPi 5.