I have a Zenfone 6 running OmniRom, and I have a black screen since I prepared for flashing a new version (I couldn't do OTA because I skipped too many intermediate versions). It happened before I did any flashing, so it is not the consequence of a failed flash. The screen does not light up at all, not even for the bootloader or the warning saying that OEM is unlocked. The system underneath seems to be working well, though, as far as I can tell. I can hear the "click" noise when it's going to standby and I can access it via ADB (and also via fastboot, when it's in fastboot mode).
I will now try to explain the circumstances that led to the black screen: I first tried several times to boot into recovery before I remembered that I haven't actually flashed the recovery and booted from a TWRP image stored on my computer at the time I installed OmniRom. Note that at this point in time, the phone was still working normally. So I tried booting into fastboot mode using power+volume up key combo, but I think I held it a little too long and it selected and executed the power off action in fastboot mode. After that, the screen did not light up anymore.
Does anybody know how I can fix that? Is it maybe some weird mode? My strategy for now is trying to fully drain the battery and see if it works afterwards (I wish the battery was still removable in modern devices...).