You can install this ROM even with a PIE Bootloader because it's flashable with TWRP.hi i have a spain version sm-g955f with root and twrp and stock version of android 9 installed.
base band version G955FXXS7DTA6
KERNEL VERSION 4.4.111-17264019 # 1 Fri Jan 31 13:39:23 KST 2020
I should go back to Android 8.
can i install your rom?