As of LineageOS 21, support for this device was migrated to joan builds. This means that this device is supported on the afformentioned version, just under this newer codename, please see joan’s page for more information.
Special boot modes
Recovery: With the device powered off, hold Volume Down + Power until the LG logo appears, then release Power for a second and hold it again until the recovery comes up.Note: Accept the factory reset prompt using the hardware buttons. If you have done everything correctly, this will not actually reset your device but instead will boot the custom recovery.
Bootloader/Fastboot/Download: With the device powered off, hold Volume Up + Power.