Have posted about this before, but doing a cleaner post on it.
SInce 4.2 the privileges for setting locale changed and you either need a rooted a phone or grant the privileges with tools from a computer.
This is done on a regular HTC One, it’s not rooted or changed in any way and the process shown here will not alter anything on the magnitude like root.
Important: Install MoreLocale2 first
I will show the PM Grant way here
What you need
- usb cable
- Have HTC Sync manager installed for the needed drivers
- ADB and Fastboot tools, either as a part of Android SDK or Minimal installation of ADB and Fastboot
First you need to hook up phone to computer with USB debugging enabled (or it will not work very well). This you do in Developer options if it’s not on already, if you can’t find developer options: read this
Edit: with 4.3 , you need to OK the debugging mode on your phone.
With a command line (on a windows computer, windows key + R and type CMD) you type (I assume with Paths and such ok, or stand in the directory where “adb” can be found). Each command is followed by ENTER.
this will set adb into shell mode, where you can enter commands directly to your phone
The prompt changes a bit, and you enter (careful with spelling and caps). Enter
pm grant jp.co.c_lis.ccl.morelocale android.permission.CHANGE_CONFIGURATION
The prompt will not show you much, just mirrors the last bit. That means it was successful, I do this with Morelocale 2 open on my phone. And then you can just change language to whatever you want, this grant stays even with a restart of the phone.