Warning - This mod could brick your router, although its unlikely, I take no responsibility for any damage caused. That being said, these changes only exist in the temporary storage, so resetting your router is enough to uninstall them.
This mod allows non-international (Chinese Mainland) versions of the MiWifi (Xiaomi) firmware to use other languages (English), as well as enabling the locale chooser. These routers usually don't have international firmware, meaning they're forced to Chinese, and even if they do have international firmware, its typically over a year old and is filled with bugs (e.g. R3P int firmware has channel issues). This mod isn't "perfect", there's still parts that are not translated.
This mod will patch the Chinese firmware running on the router to re-enable the language chooser, region chooser (so you're not longer breaking your local laws) and download the English language pack. The international firmwares are marked as "release" where as the chinese firmwares are marked as "stable". So we patch out that out too.
We then install these changes to /etc/firewall.user so they're persistant across reboots, as the changes only exist in the ram.
Right now only the Xiaomi Router 3 Pro (R3P), Xiaomi Router 3 HD (R3D) and Xiaomi Router 3G (R3G) are supported, you're more than welcome to patch this to work on other models.
To install, make sure you're on the Developer Version of the firmware with SSH enabled. Enabling this is outside the scope of this tutorial, a quick Google will find the instructions.
Install:
mkdir /etc/langmod; cd /etc/langmod; curl https://raw.githubusercontent.com/p1u3o/MiWifi-Language-Mod/master/install.sh -o install.sh; sh install.sh
Warning - This mod creates multiple bind mounts so it can patch the firmware. For some reason this can cause Dropbear not to start, however to be on the safe side this mod will start it manually anyway at each boot.
Uninstall:
umount /usr/share/xiaoqiang
rm -r /etc/langmod
rm /etc/firewall.user
reboot
Done.