Stock ROMS may display 4G instead of LTE. If it says 4G, that usually means you're on LTE.I only saw the LTE icon when I was using a custom rom (InsertCoin), a T-Mobile version (it allows you to pick your carrier during install), but never on the stock rom. That's why I'm wondering what files I need to make it work on the stock rom. Maybe the radio, I'm not too sure about flashing radios so I will do some research.
I installed your addon but unfortunately I'm getting the same error I was getting with the InsertCoin custom rom: ER05 "Invalid Sim"
Not sure what to do next. Thanks for all the info so far, it's helping me understand things a bit better.
On ARHD, I had to modify this file:
/system/customize/ACC/default.xml
<item type ="boolean" name="show_4g_for_lte">true</item>
Changing this to false did the trick for me on ARHD. I'm not sure if it's the same or similar on a stock based ROM. Good luck!