Ugh... I finally found a TOT after searching for hours on end. Pretty much every website, link, whatever for this phone is broken, gone, adware, malware. Anyway, this was all for naught.
After many, many more hours of searching I can't find any Qualcomm utility that works. QFIL, EFS, QPST, USB1, USB2, USB3, I tried everything. BoardDiag is by far the easiest to use (either v3.99 or the "2014" version both of which support the LS620). However, after it loads the diagnostic firmware to the phone nothing happens, the phone doesn't respond. In fact from that point the phone doesn't respond to anything at all and I have to pull the power for it go back in to 9008 mode.
I tried qdl in Linux as well. I don't know if it's potentially something with the emmc firehose or the raw/patch XML setup. The firehose seems correct because it does seem to read some data off the phone. However right after that it gets USB protocol errors and timeout. Then the write fails with timeout. Seems broken. Potentially this Qualcomm interface NEVER worked right on these phones. Either that or I have bad programmer/config files. I have no idea.
The phone WAS working enough to run the EDL, TWRP, and flash firmware so I believe the AP and PMIC are working fine so I'm not sure why it doesn't respond now.
Edit and update:
Well it turns out that my eMMC was totally broken and it's not the fault of this firmware, just a coincidence.
The eMMC couldn't boot at all so I figured out how to boot to download mode via SD card. From there used lglaf to attempt to write various partitions but since the eMMC is failed that didn't work out. This caused the phone to switch to booting to fastboot off the SD card for some reason. I can do more stuff from fastboot though like boot kernel images. So I modified the stock boot and recovery images to use the SD card partitions instead of the internal memory. Now I can boot the whole phone off the SD card. Only problem is that it still only boots to fastboot mode so I have to manually fastboot the boot image to start the phone every time.
I did finally flash this firmware to the SD card and it seems to work fine.