what can i do with this phone? (brightness fix?)

im dealing with this Note 4 from verizon for someone right now and i cant get to do anything with this damn locked bootloader!
due to a unrelated issue i upgraded the phone to LP and now i cant root. but to make matters worse the brightness cant be lowered. i read how to fix it but i need a custom recovery to install the zip, i cant install a custom recovery because i cant root.
i tried downgrading but i cant because of the bootloader (Bootloops at verizon logo). cant install mulitsystem because of no root because of that bootloader. its i infinite loop. as much as i want root ill settle for fixing the brightness.