Lg Aristo 2 Fastboot flash recovery - FAILED (remote: 'unknown command') I've recently been trying to flash twrp on my Lg Aristo 2, when I ran the code to OEM Unlock a device it came out with the same "FAILED (remote: 'unknown command')".
I started my phone back up and it came to a set up screen, I set up my phone and it said it was OEM Unlocked. When I try to flash a custom recovery, or run any command with fastboot at the beginning  i get "FAILED (remote: 'unknown command')" and it doesn't work. Can someone please help?
Seems fastboot is broken or disabled since Oreo.
First you have to downgrade ROM to Nougat. You can flash *.KDZ files with LGUP or LG Flash Tool.  



Then it should work as usual:


Make sure you have enabled
System Settings > About Phone > Developer Options > Enable OEM unlock,
and
System Settings > About Phone > Developer Options > Enable USB debugging  
check adb is working  

adb devices

check fastboot is working  

adb reboot bootloader
fastboot devices



WARNING: Factory reset, all data lost!  


unlock the bootloader (one of these should work)  

fastboot oem unlock
fastboot flashing unlock

if unlocking was successful, you can test recovery without flashing  

fastboot boot &lt;path&gt;/recovery.img

then reboot into bootloader and flash recovery  

adb reboot bootloader
fastboot flash recovery &lt;path&gt;/recovery.img