[LG V20 Guides, News, & Discussion] koodz:
Hello everyone, I'm a total noob but I solved a problem which I couldn't find the answer to, so I thought I'd share. Please take care following my noob advice, I'm not responsible for anything which goes wrong with your phone (and if it gets complex, I probably don't have the skills to help)!!

What was my problem?

When I went from Nougat to Oreo, my radio broke (no cell reception). However I had the files from LGUP, so I could flash "fsg" "modem" "modemst1" and "modemst2" in fastboot (as explained here) which did indeed fix my modem problem, giving me back radio and data. However, this also made the fingerprint scanner disappear from my phone's settings menu. As far as I could tell, this wasn't a problem related to encryption (as discussed in AO ROM thread a lot, which is what I'm now running), rather 'twas a problem with the firmware! So I was loving Alpha Omega, but left without fingerprint scanner since radio isn't really optional on a phone.

Solution?

Please remember, I'm a noob and have only done this for my own phone, a h910, I don't know if i will work for you or on other models!!

Basically, I mish-mashed the two modem files from Oreo and Nougat, to get both things working!

Steps I took:

1) Use Linux - I couldn't get the files to open properly in windows, and didn't find a way to write to the image files.

2) Find a stock "modem.img" file from Oreo (i searched on google "stock oreo h910 modem and it came straight up) - I think I am too new on this forum to post outside links so you'll have to search for it.

3) Find a stock modem file from nougat (I used my original LGUP dump file from nougat, renamed to .img) I'm not sure if it is important that this came from your phone or not, if you followed all the instructions on the dirtysanta root guide, you'll have this as part of your LGUP backup.

NOTE: both of these files were 86 Mb (helped me feel confident I'd found the right thing on google)

4) Create backup copies of both, and append ".img" to your LGUP "modem" file. Call the backup of your OREO modem (the one you got off of google) "MyModem.img", just to keep it clear for later.

5) Mount the NOUGAT img first in a terminal (might have to make a mount point first), for me this was like this:

sudo mkdir /mnt/modemfiles
mount -o loop /path/to/your/nougat-modem-file.img /mnt/modemfiles

You obviously have to put the file path to where you saved your NOUGAT modem image - the one from LGUP!

6) You should now be able to see the nougat modem .img mounted as a disk in "places" on your file explorer. Go there, and copy the contents into a new folder somewhere easy to find (make a folder on your desktop called NougatModem.) There are two folders iniside, one called "image" and one called "verinfo".

7) Now you can un-mount, as we have what we need from it, easiest to do by just right-clicking it in file explorer and select unmount.

8) Next we will mount the image which will become your new (hopefully working!) modem, but it has to be writeable, so using the same mount point we would do

sudo mount -o loop,rw /path/to/MyModem.img /mnt/modemfiles

Remember that "MyModem.img" should be your backup OREO image - where all the firmware works but you don't get radio.

9) Now basically comes replacing a few files in the OREO modem (which we have mounted) with ones from your original NOUGAT backup (which are in that folder on your desktop). I couldn't remember if cp command replaced things with the same name, so I used rm to remove files, and then cp to replace them once they were gone.

a) first it is the folder called modem_pr, inside image

sudo rm -R /mnt/modemfiles/image/modem_pr/

b)next were all the files in the image directory which were modem.SOMETHING

sudo rm /mnt/modemfiles/image/modem.*

10) Finally we have to replace those files and the folder with the same things from our NOUGAT folder which is on our desktop, using the copy command. I will put the commands as if you did name that folder NougatModem

a) so first the folder which we removed

sudo cp -r ~/Desktop/NougatModem/image/modem_pr/ /mnt/modemfiles/image/

b) now all the files again, using the wildcard for the different extensions

sudo cp ~/Desktop/NougatModem/image/modem.* /mnt/modemfiles/image/

So if all went to plan, you now have an image (which you can unmount), called MyModem.img, which you can flash in fastboot to the modem parition (fastboot flash modem /path/to/MyModem.img) and if it works for you like it did for me, you have cell reception, data (after putting in APN if it's needed) and fingerprint scanner all working on OREO. Again, I'm on Alpha Omega, loving the rom and now going to go play a bit.

I've not been on the forum long, but have just gained a HUGE insight into how much time people put into making guides and helping others learn (this has taken me ages haha). Thanks to everyone for your hard work and community spirit, please let me know if this works for you or if it provides any interesting insight as I really did it blind (I had no idea if it would work, and was just making some slightly educated guesses - I got lucky!). Also, if the instructions are hard to follow and you have a hint, I'm happy to edit them to make them clearer.

ENJOY!!

PS - I know the linux commands could be better haha, using more than one mount point too might have been easier, but I figured that I'd just keep it exactly the same as how I did it since I'm a noob and would be more likely to screw something up in the instructions, if I changed it without trying at the same time! ;)

EDIT: I could also upload my "patched" modem image, but not sure if it will work for other people's phones, or if it has "personal" or unique info in it (basically if it would be safe to do so) - If someone who knows tells me it'd be good to go, I'm happy to share it if it would save people from having to go through the whole process. I guess I hope posting all this will be a learning thing for others too :) Gotta have some justification haha!!