[nibs]

I spent a day battling with getting a custom ROM on my Redmi 3 and gave up. In case anyone reads this: Xioami make amazing phones for the price. This $120 USD phone outperforms my S3. But getting a custom ROM on a Xioami is getting increasingly difficult - you have to ask for permission, jump through hoops to unlock the phone and sometimes it just does not work. Xioami is the Apple of China - great UI but increasingly closed ecosystem. Their OS is called MIUI, which is basically Android with more customization options (necessary for the markets they serve). It is a great phone and OS, but it is more complex than just flashing CyanogenMod (unfortunately).

[h4waii]

This does not blanket apply to all Xiaomi devices. There are official builds of CM available for the Mi3, Mi4, Redmi Note 3, and a fully open source unofficial build for the Mi4C and Mi4S.

Unlocking their bootloader can be done officially through a request, or unofficially. Changing the recovery by replacing a single file in the EDL and retaining bootloader lock is also possible.

[tdkl]

It took me couple hours to get an unlock granted, then the unlock was done in couple minutes - it does require to read the instructions though.

After the unlock:

fastboot flash recovery twrp.img

fastboot boot twrp.img

<Couple swipes to Install the previously downloaded .zip>

Same as Nexus.