I do not guarantee that modifying your original software will not destroy your device. I do not promise to provide support to those with issues. However, this is a community and any kindness effort that you put into your inquiries and questions will likely be returned. Good luck.
As an owner of the T-Mobile D801, I realize the apparent lack of specially catered ROMs for the device. I will provide some background. It is possible to install all other G2 variant ROMs on the device, however many of these will bring with them issues. For example: ATT's (D800) extra microphone will break speaker phone on the D801, as well as cause other audio issues. Verizon's ROM is generally unstable due to the different hardware it employs. The Canadian versions, I have not tested myself, but so far have seen no Canadian-made ROMs that are better than the International counterparts.
The exception, of course, is the International variant: D802. As far as I've found, all functions on D802 ROMs work fine on the TMO D801 device. You'll just need to flash a D801 kernel over the D802 ROM.
This guide is not intended for the seasoned XDA warrior. It is simply aimed at the average D801 owner who's looking to flash some custom ROMs, only to find that he doesn't have the best selection among all the G2 variants.
PAC ROM for D802 doesn't work using this method.
Data may not work initially due to bad settings. First, check to make sure that your APN Settings are correct. If your APN settings are all set and you're still having issues with LTE vs. UMTS/HSPA+, try changing your network mode to include LTE. Of note, a build of Vanir was having issues with data at the time of writing, so if you cannot fix your issue, try another ROM.
The only thing that I've not seen in custom ROMs based off of anything other than LG's D801 stock is WiFi calling. If you use WiFi calling, following this advice will take away that feature. To retain WiFi calling, you will need to stick to near stock. Please, if I am in error about this fact, PM me and let me know, or reply below.
Your device's build.prop will identify as a D802 from now on. You may choose to edit this back to D801. Either way, don't trust OTAs or device-specific quirks like open-recovery scripts. It's your job to be a little cautious, and avoid automation that could brick your device. Always have at least one NANDroid backup to return to.
How this works:
Very simply, the most device-specific aspect of these ROMs is the kernel (boot.img). It controls very base-level functions such as managing where boot pointers lead to and providing hardware control. G2 kernels do not mix-and-match from one device to the other. After installing a D802 ROM, you now have a completely incompatible D802 kernel. You must install a D801 kernel to fix that. Afterwards, everything generally seems to work fine. If you can find any issues, report back here.
- You must have a custom recovery (like TWRP) installed.
- As far as I've seen, you also need to be rooted (IOroot method) before installing a custom recovery on this device.
- Download the D802 ROM of your choice. [Warning: PAC ROM for D802 doesn't work]
- Download a kernel made for the D801.
For stability, you may use your stock kernel for LG ROMs (backing up/restoring just "boot" in recovery --> that's the kernel), or an AOSP-friendly stock, as built by Houstonn
For features, Custom G2 is a great modified kernel. It includes a D801 version for both Stock LG-based ROMs, as well as AOSP-based ones.
- Reboot into recovery.
- [Optional, but strongly recommended] Perform a NANDroid Backup, in case anything goes awry. Backup at least System, Boot, and Data.
- Perform a Factory Reset, then wipe cache & dalvik cache.
- Install the D802 ROM, including Gapps if needed. DO NOT REBOOT.
- Immediately install the D801 kernel.
- If you ever update your D802 ROM, through .zip or per-ROM OTA, you must always flash a D801 kernel afterwards.
*It may take a while to get by your first boot. I've personally never had the first boot take longer than 2 minutes or so. If it takes upwards of 10 minutes, then try forcing a reboot by holding the power button. If the device still won't boot, something must have gone wrong. Reboot into recovery by holding the power button until the screen goes black, then hold Vol-Down & Power, and when the LG logo appears, release and re-press/hold this key combination. You will arrive at a screen offering a factory reset. Just press the power button twice, ignoring the warnings, and you will boot into recovery. Restore the NANDroid backup you made earlier.Your phone should boot now. You may attempt to try the whole thing again. Post the combo that gave you issues to this thread. Again, this has never happened to me when following the correct procedure. An issue I could see is attempting to use an AOSP-friendly kernel with an LG Stock-based ROM, or vice-versa.
If you are having issues with data, see the "Issues" section above for my recommendation: APN Settings.
I've been running D802 ROMs for weeks, without any abnormal issues, including CleanROM, Vanir AOSP, AOKP, and CM.