The steps are pretty straight forward actually and are taken partially from this post here for the H933: https://forum.xda-developers.com/sho...49&postcount=2
EDIT: The files I linked previously have been updated since I made this thread so instead of going through everything download this the US998(E) firmware, and just flash that then AOSP and whatever else instead of following the steps past #4. It fixes all the issues with the calling/data, etc that the H931(F) did.
H933 KDZ: https://forum.xda-developers.com/lg-...-h933-t3795908
US998 keep twrp: https://forum.xda-developers.com/lg-...p-zip-t3868415
H931 keep twrp: https://forum.xda-developers.com/lg-...f-rom-t3872926
1. Starting with a US998 converted H931 with TWRP, download the H933(20G) KDZ and boot into LGUP. In LGUP choose partition dl and select everything except recovery.
2. After the phone is done flashing it should boot immediately to TWRP.
3. Immediate reboot to recovery then format data, and in advanced wipe choose dalvik, system, data, and cache and wipe that as well.
4. Next flash the US998 zip and let it boot then shut it off and return to recovery.
5. From TWRP restart the phone and let it boot normally. It will bootloop and you'll need to then return to TWRP. With out doing that I was getting some weird errors with the phone not being able to Mount the cache.
6. Clean flash the phone again
7. Now flash the H931 zip in TWRP, and dirty flash your AOSP rom of choice and whatever else you need/want (gapps, magisk, etc).
If TWRP decides it doesn't want to flash anything, then choosing wipe->format data, and restarting TWRP until it does.
That should be it! Thanks goes to @Who-Lep who originally figured it out.
If you have any questions please feel free to ask. Also let me know if anything doesn't make sense and I'll try my best to fix it.