Some notes about LGUP:
1. If you choose "Refurbish", the only selection will be .tot
2. If you choose "Upgrade", the .kdz selection will be available (as well as .tot)
Therefore: if you are flashing a .kdz file, select "Upgrade" even if you are downgrading to a lower version of Android. This will allow you to select the .kdz file. After that, you can now select "Refurbish".