Working on new version to fix gapps issue - for now only core/basic will do.I followed the instructions perfectly but every time I format data in TWRP (3.5.2_11) after I flash, the ROM doesn't boot (It only boots back into TWRP again) and my internal storage gets hosed and MTP doesn't work in TWRP afterwards requiring another MiFlash back to stock. I tried flashing about 4 times with the same results.
EDIT: Nevermind. I followed these steps:
Installed ROM zip
Flashed Gapps Magisk
Factory Reset then Formatted Data
Had to install Core Gapps as there wasn't enough space in system to install Standard