See Klipper Architecture / Ecosystem how the Klipper components interact.
The host (your small computer, SBC, Sonic Pad) runs the Klipper host.
The printer-board (this thing where all the printers cables are attached) runs the Klipper firmware
Both of them will do nothing without the other. So the installation sequence is:
- Install Klipper on your small computer, SBC, Sonic Pad
- Build the printer-board firmware
- Flash the printer-board firmware
- Get its serial path
- Modify your printer.cfg so that it matches your printer AND add the serial path from No 4
- Start Klipper on the host
- Potentially reset the board
Only then your printer’s display will show anything meaningful (if you have done it right).