[LG Leon ROMs, Kernels, Recoveries, & Other Develop] al345464:
Quick Guide to TMO LG Leon CM12.1 Install (10E stock & LGH345K)

Here's what I did to get this working - and no one has put together a detailed guide for TMO M345 (LG Leon LTE). Build works great with LG Leon on stock T-Mobile with 10e boot and LGH345KT build. Couple of pointers on your way (Info below is for T-Mobile only - stock build and roms (here):

Drivers: http://androidmtk.com/download-lg-usb-drivers

Battery: really annoying to remove, so needed to practice - volume up, volume down and power off are located on back only (T-Mobile Guide)

Disable OTA updates: within phone dial: 277634#*# And then navigate to wifi section of the menu and you should see the option of OTA updates - Disable(More here)

Mount SD Card: Buy an SD card and insert into slot that has at last 16 GB - those are like $5 on sale. You will not be able to make TWRP backups along the way without it. LG Leon on T-Mobile build leaves little room for mods.

Don't connect to wifi until you have root: Do not use wifi until you have root established. T-mobile has programmed the phone to automatically upgrade within 2 minutes of wifi. I had to reflash stock several times to stop this from happening. Easiest way is to not connect to wifi until you have worked out root.

Kill Lookout Anti-virus: Kill this very annoying process going into the Settings>Apps>All>Lookout. Lookout is *hidden* by T-Mobile so it doesn't appear in your All Apps. Disable Lookout Auto-update within the Lookout program because it kills any of the modifications you are making in real-time.

Developer Mode/OEM Unlock/Unknown Sources/ADB Debug. You must enable all of these - they are found in the Settings and to be able to see them you must enable developer mode via tapping the build button (located in "About Phone...Build Number") several times.

Disable ADB scanning/Android Administrator. I turn these off just because they have caused many headaches in the past while moving a T-mobile device to CM 12.1

Getting Root (#): Needed to use NewKingrootV4.60_C132_B234_xda_release_2015_11_23_105243.apk as none of the root, chainfire/One-Click-variants worked Don' like KingRoot at all - so will be removing shortly. Used it only for the next steps. I just KingRoot APK to my computer and used USB cord to transfer to the phone, and then installed from the phone itself. KR needs wifi to work, so you can connect now.

Download and Recovery Modes: Since volume up and down and power are located close to one another - i found it difficult to boot into recovery from powered off state [hold vol own/power down, then on LG Logo (keep vol down, but release power once), and then hold power vol-down again until boot]. You might need to practice.

Deny T-Mobile Adapt Process: Within 2 minutes of wifi - the phone begins pinging com.tmobile.pr.adapt (More info about this annoying process) to report about your phone status, rooting, and app mods. Kingroot should offer to block request. Deny the adapt process, and Lookout.

Flashing TWRP: Needed to download twrp manager from Play Store and then install default "C50" twrp from there. That version will work but appears to be different than the "official" version. I didn't find a flashify or odin solution for LG Leon T-mobile

Make a twrp backup Once you have a TWRP Manager "c50" installed make a backup immediately. (official c50 twrp) I failed at this process at least 6 times, and were it not for my backups this entire process would be a lot more difficult - trying to re-flash stock is a real pain. Turn off wifi - you won't need it anymore.

Install the "correct" Blue TWRP Img: From new CM12.1 LG Leon CM12.1.... Download to your computer and then transfer to phone via USB. Reboot into recovery. Notice that IMG file *doesn't appear* - this was a big *duh* moment since i remember that to expose twrp IMGs you need to click on the "IMG" or "install image" from the Install Menu button. Reboot into the new TWRP and make a backup. Be sure that your target is the external card (and not the internal storage). Wipe Davik Cache.

Remove SD card before installing new CM12.1/Gapps. You will want to force the installation to take place on the internal partition. From LG TMO main screen go to settings, and then storage and then unmount the card. Or just take the card out from the back of the phone when it is powered off.

Install CM12.1/TK GApps. Now you should be ready to install androidforums.com/threads/rom-5-1-1-ms345-unofficial-cyanogenmod-12-1-for-lg-leon.928887/ - note it take about 5 minutes to boot (long). You will need to install a smaller package (less than 400mb) or you'll get a Code 70 error which means there is not enough room on the "internal" file system. Just install the Small Modular to get this going. I tried with the full stock and other versions and it just wouldn't work.