That's not a problem with the time of reply, you never know what time zone people are in. Anyway try this Oreo rom. I thought I read that you can flash the H990DS rom on the H990n just one of the sim card slots will be grayed out or not work. I am thinking maybe it's the Oreo rom you were using, because this should work.
If you are having issues downloading the rom you can try this download manager for Firefox.
Turbo Download Manager
2. Then copy all the files to your micro sdcard
3. Reboot into twrp
4. Click Wipe
5. Format Data Partition (this will erase your internal storage on the phone)
6. Click back and reboot into recovery again. aka twrp
7 Flash in order
A. Your version Of Stock Oreo 8.0 rom
B. ezV2020 Kernel
C. Magisk v21.4
D. Twrp (The twrp img file you can flash with twrp you just need to select Install Image, select the file and choose recovery)
8. Reboot into system, run setup
9. Magisk app v25.2, does not work with Oreo. You can update Magisk to v22.1 it works.
10. Good idea to reinstall your EFS to get cell signal working see FAQ & Troubleshooting guide. Under "Is there a guide I can root my Lgv20 with Dirtysanta?"
11. Optional you can DeGoogle if you want. Under I want to "DeGoogle after Auto_Debloat, can I do that?"
I am following the steps now. (I was too late yesterday)
Currently it seems to be stuck after flashing Auto_Debloat_Lgv20_msm8996_Oreo_v8.x_flashable.zipper (should I have rebooted with new TWRP?).
the log shows:
Auto_Debloat Script completed Please wait....