Some community forks of checkm8 tools explicitly add D11AP support:
Look at the back of your phone or the SIM tray for a code starting with "A" (e.g., A1660, A1778). Use DFU Mode: Put the device into Device Firmware Update (DFU) loader for iphone9 2-d11ap not found
Sometimes the error is transient. Force the device into a different state: Some community forks of checkm8 tools explicitly add