6.] Try this install variation:
After »Installing a custom recovery using dd« Step 5. “factory reset”, remove the battery for a few seconds…
Then reinsert the battery and boot manually into TWRP Recovery with the following key combination:
With the unit turned off, press and hold VOL(-) and POWER buttons until the LG logo appears, then release Power-Button for one second and press and hold both buttons again until the TWRP Recovery Menu occurs.
By the way: My d855 is not rooted and /e/ OS e-0.7-n(ougat) works as well as LineageOS 16.0 or Panta’s unofficial build e-0.7-p-20200xxx.