Slow fading LED should be good evidence that it has a boot loader on it. If it has a boot loader, the rescue procedure should work.
Have you seen the Troubleshooting page? But that is only a Windows problem...
https://librepilot.atlassian.net/wiki/spaces/LPDOC/pages/12812343/TroubleshootingBootloader is there but not working, other cables and computers tried. That leaves the next most likely thing being a solder blob or open in the USB area. Magnifying glass time... Has this CC3D USB ever worked?
Windows sees it enough to know something was plugged in. That should be telling us that USB is talking somewhat.
Ahh Debian! What does lsusb say? More importantly, what does dmesg say? FYI: you would run lsusb from the command line with CC3D unplugged, then plug in CC3D wait 10 seconds, then run lsusb again and find the line that got added. For dmesg, unplug CC3D, run 'sudo dmesg -C' from command line to clear out the current messages. Plug in CC3D, wait 10 seconds, and run 'dmesg' from command line. Post dmesg here. My dmesg looks like this (I obscured the serial numbers which is way beyond necessary):
[3436187.880040] usb 2-1.3: new full-speed USB device number 45 using ehci-pci
[3436187.975001] usb 2-1.3: New USB device found, idVendor=20a0, idProduct=415b
[3436187.975006] usb 2-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[3436187.975009] usb 2-1.3: Product: CopterControl
[3436187.975012] usb 2-1.3: Manufacturer: openpilot.org
[3436187.975014] usb 2-1.3: SerialNumber: 48FFxxxxxxxxxxxxxxxxxx67+BL
[3436187.976708] hid-generic 0003:20A0:415B.004D: hiddev0,hidraw2: USB HID v1.10 Device [openpilot.org CopterControl] on usb-0000:00:1d.0-1.3/input0
[3436193.831307] usb 2-1.3: USB disconnect, device number 45
[3436194.028058] usb 2-1.3: new full-speed USB device number 46 using ehci-pci
[3436194.122903] usb 2-1.3: New USB device found, idVendor=20a0, idProduct=415b
[3436194.122908] usb 2-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[3436194.122912] usb 2-1.3: Product: CopterControl
[3436194.122914] usb 2-1.3: Manufacturer: openpilot.org
[3436194.122917] usb 2-1.3: SerialNumber: 48FFxxxxxxxxxxxxxxxxxx67+FW
[3436194.123647] cdc_acm 2-1.3:1.0: ttyACM0: USB ACM device
[3436194.126130] input: openpilot.org CopterControl as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.2/0003:20A0:415B.004E/input/input48
[3436194.126607] hid-generic 0003:20A0:415B.004E: input,hiddev0,hidraw2: USB HID v1.10 Joystick [openpilot.org CopterControl] on usb-0000:00:1d.0-1.3/input2
Note there is both a:
[3436187.975014] usb 2-1.3: SerialNumber: 48FFxxxxxxxxxxxxxxxxxx67+BL
and a:
[3436187.975014] usb 2-1.3: SerialNumber: 48FFxxxxxxxxxxxxxxxxxx67+FW
Yours may only have the BL line.
My lsusb looks like this:
Bus 002 Device 048: ID 20a0:415b Clay Logic CopterControl
I can say that bad USB cables are close to the top of the list of problems, but it sounds like you have tried other cables. I would also try a different computer and you have done that. So I would do Troubleshooting procedure, uninstall all versions of OpenPUlot and LibrePilot and reinstall just the LibrePilot version you intend to use.
If that fails, there is a procedure to reinstall bootloader when it is not working, but you need an FTDI and a hand made cable from FTDI to CC3D MainPort. Of course this won't fix hardware problems. The top part of the same page as before links to off site CC3D bootloader instructions. Use the archive.org link:
https://librepilot.atlassian.net/wiki/spaces/LPDOC/pages/5669026/Firmware+Tab#FirmwareTab-Updatebootloader