Get LineageOS for the LG G4 (T-Mobile)
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.