Your iPhone 8 might actually be in Recovery Mode (showing a cable pointing to a computer) while the software expects DFU Mode (black screen, but electrically active). In DFU mode, the device asks for a different loader signature (iBSS) compared to Recovery mode (iBEC). If your tool sends a Recovery loader to a DFU device (or vice versa), the device rejects it and the tool reports "Loader not found" as a generic fallback.
Paradoxically, the iPhone 8 (d101ap) works best on Linux for low-level loader operations. If you are on Windows or macOS: Loader For Iphone9 3-d101ap Not Found
If you are a reverse engineer or security researcher, you are not constrained by pre-built loaders. You can generate a custom loader for d101ap using: Your iPhone 8 might actually be in Recovery
Once the custom loader is uploaded, the “not found” error becomes irrelevant—you are the loader. Once the custom loader is uploaded, the “not
Warning: This requires deep understanding of ARM64, Apple’s SecureROM, and the A10 exception vectors. Do not attempt on your daily driver.