[OnePlus 5 Questions & Answers] Pseudorando:
Hi XDA!

(tl;dr - The "specific technical questions" are in the last section. )

I'll spare everyone a detailed explanation of what I've been through with this phone in the last few weeks, except to say that I have exhausted all simple solutions.

The current state of the phone is that both its main and recovery partitions hang with a white LED.

There are two states in which I understand it should at least register to a USB host as a visible device, whether or not proper drivers are installed (though I have tried many drivers as well):

1. FastBoot

I can Power+Vol-Up into the FastBoot menu, which appears and operates, but there is no contact with the computer over USB.

2. Qualcomm

I can Vol-Up then plug-in which should boot into "Qualcomm mode" (a.k.a. EDL mode?), but there is also no indication of a low-level device reporting itself as "Qualcomm" or "QHUSB_BULK", or the presence of any device at all on four different laptops, both Windows (via Device Manager) and Linux (via lsusb).

2a. Each of these cable/port/laptop combinations do work for charging the OnePlus 5

2b. The same cable and ports function properly for FastBoot/data with another phone.

2c. The vol-up+plug-in method for inducing "Qualcomm mode" does appear to do something, which is that it stays on a black screen doing nothing instead of booting upon plug-in, which is what it does with no vol-up. (Before, plugging it in would send it to the "battery charge" screen, but now, having broken it further, it boots into white-LED failure).

Failure modes eliminated:

1. The USB-C/headphone port assembly was also replaced because the previous one had been unstable for a while and I wanted to ensure that a loose connection was not the cause of the FastBoot issue. The new port is now solid and reliable. I also inspected the internal ribbon port where the ports connect to the board to ensure that the tiny fragile connectors were not damaged during the swap.

2. I have also tried all methods of gaining access after disconnecting the battery for a while, and attempting to connect before pressing any keys.

Specific Technical Questions:

1. Is there another way to get the OnePlus 5 into EDL mode other than Vol-Up+cable-connect? Such as with an EDL cable or by shorting test points on the board?

2. Is there a way to boot from another device, such as via OTG, connecting to a port on the board, or using special service hardware?

3. Is it possible to communicate with a USB device even when it does not appear to low-level USB inspection tools running on the host machine, such as lsusb (Linux) or various Windows USB utilities that scan all attached USB controllers for registered devices? (Or shall I continue to interpret the phone's invisibility to any such tool as an indication that no possible driver could recognize it, and thus avoid trying the dozen or so candidates I've collected?)

4. Is it theoretically possible for (buggy, incorrect, malicious) software being written to the recovery partition to break USB data connectivity or impair FastBoot?

5. Is it possible that a hardware issue might break the USB port for data, while allowing it to function correctly for charging?

6. Are there any other suggestions for a way forward I haven't considered here?

Thanks!