1  The phone must be network and factory unlocked.
   2  I need to know the phone's IMEI.
         So that I can make sure it will work with my carrier.
         (Published compatibility data is confusing, conflicting and not dependable.)
   3  The phone must have an Unlocked Bootloader
   How to Find Your Phone's IMEI
      Dial "*#06#" on the phone.
   How to Tell if the Bootloader is Unlocked
      Turn on Developer Mode
         Settings -> [System] -->About phone --> tap on "Build number" 7 times
      Examine the developer option "OEM unlocking" setting
          Settings --> [System] --> [Advanced] --> Developer options --> OEM unlocking,
          and move the button to the right
      If "OEM unlocking" is absent or grayed out or you can not move the button
          you do NOT have an unlocked bootloader