[Xiaomi Mi A3 Guides, News, & Discussion] Kaissner:
I had this device for two days now, one of the first things that I tried was to install a custom ROM and I was surprised of how hard it was to do, so after a lot of trial and error I managed to install those two ROMs so I wanted to share how I did it so nobody has to suffer like I

Okay so I have tried two methods, one worked for Pixel Experience and the other for Lineage OS, there are probably better ways to do this so be sure to reply to this thread if you find another ways to accomplish this!

IMPORTANT!:

1. I did the two of this methods with the stock ROM with a minimal setup (skipping wifi, no google login, no fingerprint, etc).

2.You need to have the bootloader unlocked.

3. Im not responsable if you brick your phone or lose your data, do the following steps if you know what you're doing and always back-up your data!!!

Files used:

TWRP link (Download both the img and the zip)

Pixel Experience link

LineageOS link

Gapps link

Magisk 20.1 link

Encryption patch (patch_no_fde10) link

Method 1 (Tested succesfully with Pixel Experience):

Thanks to ElSuperFullHD for creating an awesome guide in how to install Pixel Experience!

How to install Pixel Experience in Xiaomi mi a3 (Spanish guide)

1. Start your phone in fastboot mode.

2. use fastboot getvar current-slot (Check if phone is in slot a, if it isnt change it to a using fastboot set_active a)

3. Flash custom recovery (in this case I used TWRP) with fastboot flash boot twrp.img

4. reboot using fastboot reboot (NOTE : Before hitting "Enter", long press Vol + on your device until you see the Android One logo. By doing this your device will be forced to boot into Recovery and not into System).

5. When TWRP starts, move and flash TWRP zip (This will make the recovery to stay) and reboot into recovery again (Long press Vol + when the device starts until you boot into recovery).

6. Go to advanced wipe Dalvic cache, Data and System.

7. Install Pixel Experience ROM and TWRP zip again and restart to system.

8. You're done, enjoy!

Method 2 (Tested succesfully with LineageOS):

Thanks to suschmania for your extremely helpful comment, I wouldnt have figured how to install LineageOS without him!

1. Start your phone in fastboot mode.

2. use fastboot getvar current-slot (Check if phone is in slot a, if it isnt change it to a using fastboot set_active a)

3. Flash custom recovery (in this case I used TWRP) with fastboot flash boot twrp.img

4. reboot using fastboot reboot (NOTE : Before hitting "Enter", long press Vol + on your device until you see the Android One logo. By doing this your device will be forced to boot into Recovery and not into System).

5. Once in TWRP copy TWRP recovery zip into the phone and wipe Dalvic cache, Data, Vendor and System.

6. Install the ROM and TWRP recovery zip (This will make the recovery to stay).

7. Reboot into recovery (twrp shows the warning no os installed, continue anyway).

8. The filesystem will be decrypted (All folders corrupted) dont worries, just go to advanced wipe and wipe internal data, once that's done copy Gapps, magisk and the encryption patch into the phone).

9. Flash Gapps, magisk (Optional) and encryption patch.

10. Reboot to system (It may take up to 10 minutes to start so give it time, if more than 10 minutes passes see step 11).

11. In case of bootlop boot back into recovery and format data (its the one where you need to write yes to format), after its done reboot to system again.

12. You're done, enjoy!

I hope this guide was helpful to you, good luck!