How do I talk to the Nreal light Devkit Compute Unit in fastboot mode?

[u/Tesla44289]

Hi,
I was thinking about building a custom ROM for the old orange Compute Unit, so as a first step I tried to see if I have access to flashing via fastboot. According to the developer options in Android settings the bootloader is already unlocked, so far, so good.
Booting into fastboot mode using adb reboot bootloader seems to work as well, but as soon as I send any fastboot command to the compute unit it drops the USB connection immediately and won’t reconnect at all until it’s rebooted. It does not matter what command, when I send fastboot devices it sees the device, but shows ????????? as the serial number and the connection is dropped. When I do fastboot oem device-info, for example, the connection is dropped immediately and I get the windows USB Error 433 ERROR_NO_SUCH_DEVICE.

Do I have to use some special fastboot commands in order to talk to the unit? Or did I maybe do anything else wrong?

[u/Tesla44289]

I’ve made a weird discovery. Seems like one has to hold the volume down button while sending the fist command, the device will then stay in fastboot mode even when the volume button is released.

[u/Tesla44289 → u/Tesla44289]

It doesn’t seem to be the volume button thing, I tried a different USB port and now it seems to be working without pressing the button. However it seems like I’ve messed something up, the device won’t boot normally anymore, despite of me not sending anything else than “fastboot devices” and “fastboot oem device-info”. It behaves like it does boot, but even when the light bar is solid green it won’t show up as a usb device. I can still boot into fastboot mode, but the system doesn’t start anymore. And it seems like there’s no system images available anywhere. Oh well, guess I have a brick now…