I own the Ender 3 Pro BUT, I have the silent motherboard 32-bit and installed with the firmware: "Ender-3 Pro_HW4.2.7_SW2.0.9.03_SpritExt_H300" because it seems like its the only one meant for the extruder pro kit. It complains that the BL-Touch is not attach to it. I can see it in Octoprint error message and gcode terminal.

• Firmware Source: https://www.crealitycloud.com/software-firmware/firmware?type=2

With the default firmware on it, it did manage to start the print till its heated to 228°C, but Octoprint couldn't proceed after the printer heated. It just waited till infinity.

Additionally the Display is not working at all, its beeping and mid beeping a louder beep is repeating every second. Not sure why, but the display claims to support Ender 3 Pro, Ender 3 and Ender 3 v2.

More Sources:

• Display: https://www.amazon.de/dp/B09292H22C
• Extruder kit: https://www.amazon.de/dp/B0B4NHNJ7K
• Silent Mainboard: https://www.amazon.de/dp/B07TY3HQ5H

What firmware would be the correct one for the extruder? Should I return the Display?

Silent Mainboard did work with the stock-extruder. It stopped working with Octoprint after replacing the extruder with the new one, but seems to heat and move correctly.