If you ask about the workaround, when GUI is missing in recovery mode, then my belief's the method is universal. Nevertheless recovery must be successfully flashed and working, even though without GUI, but providing adb interface for commanding in...
Someone else posted elsewhere the default password.
It's either 123456 or 000000 IIRC
Sent from my LG-D855 using XDA Premium 4 mobile app
It worked as mentioned.
I entered 123456 and it got unlocked :)