== important ==
I was unable to flash and reboot into TWRP recovery after applying the official Samsung update from March, which updates Android from 10 to 11. Reboot into recovery would not work and I would always end in a boot loop.
I had to downgrade to Samsung's official Android 10 and used the binaries from January for that: https://samfrew.com/es/model/SM-A515F
After that, flashed TWRP again and was able to boot into recovery right away as it should be
Your message and the one written by "hargitomi" caught my attention, and I would like readers to be aware of few important things that the Admin or the creator of this great work did not talk about. I have interest in investigating why you got the bootloop on Android 11.
1. There is one information you did not supply: you did not tell us the complete code of the Android 10 stock firmware you had before upgrading, neither did you tell us the code of the Android 11 stock firmware that failed you. Inside each code you can find the version of the bootloader of the firmware which is very important.
2. The Admin did not tell us the complete code of the firmware he had used in his experiments. He just said "A51...CTJ1" but the most important character is missing. The only clue I have from his statement to know that the firmware bootloader version he used is 4, is when he said: "...Android security patch level: 1 October 2020". All October security patch of Android 10 of any country has a firmware code as "A515...4CTJ..."
3. Now, using my common sense to investigate, I found out that all firmwares with the code "A51...CTJ1" have the number "4" and they are written as "A51...4CTJ1". So reading from the right end to the left, the fifth character is the version of firmware's bootloader. I strongly believe that the Admins' experiment was based on bootloader version 4.
4. This means, if you upgrade from Android 10 with bootloader version 4 (A515FXXU4CTJ1 or A515FXXU4CUA1) to Android 11 with the same bootloader version 4 (A515FXXU4DUB2), and following the Admin's instructions correctly, you shouldn't have any boot loop. But if you upgrade to Android 11 with a different bootloader, version 5 (example USA: A515U1UES5BTL1), then you will have problems with boot loop because the Admin's experiment was based on bootloader version 4.
5. So many countries in Europe hardly change the versions of the bootloader and the advantage is that you have more freedom to install many firmwares. But be very careful if you are always using firmwares from the USA because Android 10, for example, can have several upgraded versions of bootloaders and I think once upgraded, downgrading a bootloader can easily brick your device. But when you said you downgraded from Android 11 to Android 10, it looks like the two firmwares you played with successfully have the same version of bootloader. It is not the operating system that matters, but the versions of the bootloader.
6. Using your link as an example, which I believe you were reading in Spanish... https://samfrew.com/es/model/SM-A515F go to Europe - Spain and choose PHE, you can see that both Android 11 (A515FXXU4DUB2) and the last update in January 2021 of Android 10 (A515FXXU4CUA1) both have bootloader version 4, and therefore should be compatible with the Admin's experiments. Identifying the version of a firmware bootloader helps you to avoid problems when upgrading. I am still waiting to receive my device, then I will try it and tell you the results of my findings. But in the end, after playing with my device, I think I will keep Android 10 because in Android 11 so many things that I like were removed.
7. As the Admin says, step 6 is very important. If you can not go directly from the downloading flashing mode to the newly flashed custom recovery TWRP and finish up the rooting process, you will not be able to boot system. Your device will hang (soft-brick). So before you do any flashing, it is advisable to do the following testing first and be confident...
- Put your Galaxy device into downloading mode by pressing the following combination keys: VOLUME DOWN + POWER + HOME.
- If your device battery is removable, then you are lucky. By simply pulling out the battery you force the device to switch off. Insert battery again and press the following combination keys: VOLUME UP + POWER + HOME. This will take you straight to either the existing stock recovery or the newly flashed custom recovery.
- If you have no removable battery device, press the following key combination to force device restart: VOLUMES UP & DOWN (center key) + POWER. As soon as the downloading screen disappears, quickly press the usual combination key to enter recovery, VOLUME UP + POWER + HOME. Maintain these pressed until information about recovery flashes on the screen or you see "Installing System Updates..." if it is a stock recovery. Then release all keys and press either Volume Up or Down to clear the Android icon that prevents you from seeing the stock recovery menu. That's it!
I performed the above operations without removing the batteries from my old Galaxies (J710MN/DS and N910W8) and it worked for me in both devices.
On my 2019 Galaxy Tab Active Pro, I only have to press: VOLUME DOWN + POWER until the stock recovery screen appears, then navigate to "Reboot to bootloader" (Downloading mode). After flashing, I can go directly from the downloading mode to the stock or custom recovery by pressing VOLUME UP + POWER until I see the Android logo, then release.
Greetings from Canada.
======== UPDATE: 30-APRIL-2021 =========
I have concluded all my experiments, and now I can confirm that the "twrp-a51-3.5.0_10-1_ianmacd.tar" on this website only works for Android 10 as instructed by Admin. This does not for Android 11. For Android 11 you have to flash a different file called "Twrp+vbmeta_A11.tar". Details are given in the following link: https://forum.xda-developers.com/t/...-sm-a515f-one-ui-3-0-dub1-android-11.4231543/
I have re-written the Admin's instructions in such a manner that clears the minimum doubts. Again, below are the steps for those who are still confused:
Flashing TWRP & Rooting on Galaxy A51 Android 10 Q:
1. Make sure the bootloader are unlocked. OEM unlocking option should be greyed out (connect to Wifi to make the OEM unlocking visible, otherwise it will be impossible to flash TWRP). Do not forget to copy all files (TWRP, Disable_Verity and Magisk) to your SDcard because you need to wipe data before rooting & that will delete any files in the internal storage. If you watch the video the Admin flashes his files from the SDcard storage.
2. Enter Download Mode: Turn device Power Off. Connect one end of USB cable to PC. While pressing both VOLUME UP + VOLUME DOWN keys, connect the other end of cable to your device and maintain both volume buttons pressed until the download mode appears after few seconds, then release the buttons.
3. Open ODIN, IMPORTANT!: Uncheck "Auto Reboot" in Options! (this prevents it from rebooting to an encrypted system that will definitely hang in a boot loop).
4. Load "twrp-a51-3.5.0_ 10-1_ianmacd.tar" as AP in ODIN, then click start to flash.
5. TWRP is now successfully flashed to your device! Several steps before you can properly use the device. Now unplug cable from PC and manually reboot directly from ODIN mode to the newly flashed TWRP custom recovery as given in step 6 below.
6. DO NOT SKIP THIS STEP! Press and hold VOLUME DOWN + POWER Keys for about 10 seconds to force a "Restart". When the screen blanks quickly release both buttons for a second and press VOLUME UP + POWER keys before Samsung Logo appears, and keep pressing them until TWRP Custom Recovery Mode or the Stock Recovery Mode appears.
7. Select Wipe -> Format Data -> type 'yes' and confirm (this operation will remove encryption from the internal storage and also wipe everything stored in it).
8. Select Reboot -> to Recovery
9. Select Install -> select Disable_DmVerity_ForceEncrypt_03.04.2020.zip -> from storage location (SDcard) Swipe to confirm Flash.
10. DO NOT Reboot to System until your device is manually flashed with Magisk (rooted).
11. Select Install -> Storage location (SDcard) -> Magisk-v21.2.zip or the latest -> Swipe to flash.
12. Select Reboot -> to System (Be patient, this system reboot takes longer than normal).
13. Connect the Device to the Internet
14. Open the automatically installed Magisk Manager App ( If you can not see it, just wait for a moment).
15. Done! Now you can use "Root Checker" to confirm the existence of root, Enjoy!
16. Do not forget also to verify that BusyBox is installed, to be fully rooted.
============= FURTHERMORE ==========
I followed the instructions of the video in the link below to create my own flashing file to remove the annoying "bootloader unlock" warning message every time you reboot. Make sure that the bootloader zip you want to use is from your original firmware currently installed on your device to avoid the incompatibility of bootloader versions (very important). See the attached files & good luck.