[Xiaomi Redmi Note 4 Questions & Answers] Rigadelt:
Hi. When I first installed LOS 18.1 I had problems with fingerprint not working, so I have written a detailed guide how to fix it. Just a disclaimer - I am not responsible if you somehow break your phone while following this guide. :D

I am also a noob on custom ROMs, but I have done the exact same steps, and my phone appears to be working fine, so you should be all right too. After all, these steps are almost identical to all custom ROMs installation instructions, the difference is that this time we use OrangeFox recovery instead of TWRP, because LOS 18.1 seems to work better with it.

NOTE:

When I used this method myself, I went back to latest MIUI ROM. I don't know if it is necessary, but I think everything should work fine without reverting to MIUI. If you would like to try fixing it without installing MIUI ROM, then go to the first reply below for a simplified guide. Nevertheless, I recommend reading the full guide anyway, just to get a better understanding of what steps you will have to do.

Also, some steps can be skipped because probably many of you have already done them when you were installing LOS or other custom ROMs. I have only tested this fix on LOS 18.1 but it might work on other custom ROMs too, I think.

I've written this guide while following OrangeFox recovery guides, and getting help from Redmi Note 4 users on Telegram groups.

FULL GUIDE (INCLUDES GOING BACK TO MIUI):

1. Install ADB + Fastboot in your PC (I assume you use Windows 10).

Download these files:

SDK platform tools: https://dl.google.com/android/repository/platform-tools-latest-windows.zip

Google USB Driver: https://dl.google.com/android/repository/usb_driver_r13-windows.zip

I am not sure if Google USB Driver is necessary, but install it anyway because I had it installed too.

For installation instructions, use the attached "ADB Fastboot installation.txt" file.

You can check this video for visual guide as well:

At this point I recommend backing up important data (photos, videos, documents, SD Card, etc.) from your phone to PC, Cloud or other safe storage.

2. You will need to go back to latest MIUI ROM. Use this page for instructions: https://c.mi.com/oc/miuidownload/detail?guide=2

If your Mido is global, then download "Redmi Note 4X Latest Global Stable Version Fastboot File Download" from (STEP 2).

VERY IMPORTANT! When flashing MIUI, make sure you select "Clean all" option. DO NOT select "Clean all and lock" (STEP 5).

3. After successful flashing, boot into MIUI. You may encounter this error when booting up MIUI 11: "Find device storage corrupted. Your device is unsafe now." This error also means that Wi-Fi and Bluetooth will not work. Don't worry, this will be fixed.

4. Next, download these files and put them in your SD Card (for example, Download folder).

(note: some zip file names written in this step will be outdated because Mido is still maintained - always make sure to check, download and use latest updated files).

OrangeFox recovery

(R11.0) for mido:

https://dl.orangefox.download/5f14b74f26d98d90b476a532

Latest mido firmware

:

https://xiaomifirmwareupdater.com/d...4XGlobal_V11.0.2.0.NCFMIXM_83170d3e3a_7.0.zip

LineageOS 17.1 with 3.18 kernel

(you will need to install it first):

https://github.com/zeelog/OTA/releases/download/27.0/lineage-17.1-20201214-UNOFFICIAL-3.18-mido.zip

LineageOS 18.1

:

https://github.com/zeelog/OTA/releases/download/41.0/lineage-18.1-20210417-UNOFFICIAL-mido.zip

GApps - "MindTheGapps arm64"

was recommended by LOS Team for LOS 18.1 when I wrote this guide (before installing ask the ROM maintainer or users if this is still the recommended version of GApps):

MindTheGapps-11.0.0-arm64-20210412_124247.zip | by Alessandro Astone for Generic Device/Other

Download GApps, Roms, Kernels, Themes, Firmware, and more. Free file hosting for all Android developers.

androidfilehost.com

Also don't forget to download "persist.img" file attached below.

5. Now, make sure that your phone is charged and has more than 80% battery (just to be safe).

Also note that after the following step, you won't be able to boot to MIUI anymore, so make sure you have made a backup of your files.

Install OrangeFox recovery using this guide:

Installing OrangeFox Recovery

wiki.orangefox.tech

6. Now, follow the instructions written in the attached "Fingerprint fix and MIUI errors" text file. (note: some zip file names in step 3 of this text file will be outdated because Mido is still maintained - always make sure to check, download and use latest updated files)

7. Finally, follow the instructions written in the attached "Readme - LOS 17.1 and 18.1 installation" text file, you should start from step 4. (note: some zip file names in step 1 of this text file will be outdated because Mido is still maintained - always make sure to check, download and use latest updated files)

Good luck!