[Samsung Galaxy A21s ROMs, Kernels, Recoveries, & O] grccorps:
This is Android 12 ROM built from Google's AOSP sources released on October 4, 2021. The sources are based on the Lineage OS for A21s, with some modifications for Android 12.

NOT WORKING:

Samsung Proprietary Apps (Samsung Health, etc.)

VoLTE & VoWifi (Due to Samsung's twisted & wicked IMS service)

Auto Brightness (The phone doesn't have the sensors for it anyway)

ExFAT-formatted SD Card & OTG (there are legal problems associated with it.)

Working but buggy or not tested:

Audio volume is smaller than usual (WIP)

RIL starting up late on very rare occasions. If telephony doesn't work after reboot, please allow up to a minute.

Cell broadcast (emergency messages) is working in South Korea, but not tested in other countries

Working, but needs installation of additional apps:

NFC, Screen Sharing, Wi-FI Direct works, but needs installation of additional apps to work

Browser app is not installed by default. Installing Firefox or Chrome from Google Play is recommended

GPS & Location services don't work when GApps are not installed.

This ROM is not compatible with TWRP due to File-based encryption.

The ROM is NOT ROOTED by default. In order to root it, install Magisk from official source.

WORKING:

Everything else not mentioned above

p.s. ADVANTAGES WHEN COMPARED TO GSI Android 12:

Based on official release, whereas GSI is based on Beta 5

Working MTP

Working NFC

Working Cell Broadcast

Fixed Fingerprint removal bug

Camera works up to 48MP (GSI camera is fixed @ 12MP)

Double-tap-to-wake is working

Model number correctly matches with the actual device (shows SM-A217N instead of AOSP on ARM64)

Updated kernel graphics driver to the latest from ARM

1. BEFORE INSTALLING, make sure that you have UNLOCKED the bootloader of your device. This is a great guide that show how to do it. Also, the phone must be on the Stock ANDROID 11. If you are on binary U6/U7, please use the recovery tar for U6/U7.

2. Download the Lineage Recovery, ROM, Google Apps, ADB, and Odin. Unzip ADB and Odin to somewhere appropriate. Save the ROM images to the folder where you unzip ADB/Fastboot

- ROM: super.img. boot.img, dtbo.img, recovery(U5), recovery(U6), recovery(U7)

- ADB and Fastboot

- Odin

- Kernel Source

- Google Apps(Flame)

WARNING: A BUG WHICH CAN POTENTIALLY LEAD TO BOOT LOOP ON U7 WAS FOUND. IF YOU ARE ON U7, PLEASE DO NOT FLASH THIS ROM UNTIL THIS IS FIXED.

3. Enable USB Debugging on the device. Go to settings->About phone->Software information, and tap the build number several times until you see the notification that the devloper settings have been enabled. After enabling developer settings, go to settings->developer settings and check USB debugging.

4. Open Command Prompt, and type "cd <the path where you saved ADB to>".

5. On the phone, start holding down the Volume Up and Down keys. KEEP THE KEYS PRESSED UNTIL THE PHONE REBOOTS AFTER YOU TYPE THE COMMAND IN THE NEXT STEP.

6. While holding the keys down. type in the command "adb reboot recovery" on the command line.

7. After the phone reboots into download mode, press volume up to continue. Make sure that you see the "OEM LOCK: OFF" before continuing.

8. Open Odin. After opening Odin, click on AP, and select the Lineage Recovery Tar file that you downloaded in the step 2. After that, click on Start.

9. After a few seconds, if everything goes well, Odin should show "PASS" and the device should reboot into Lineage Recovery. After the device enters recovery, tap on Advanced->Enter fastboot. In some cases, touchscreen may be unresponsive or slow. If that happens, use Volume Keys to navigate and Power key to select. KEEP THE DEVICE CONNECTED TO THE COMPUTER.

10. After choosing Enter fastboot, type the following lines in the Command Prompt and press enter:

10-1. "fastboot flash boot boot.img" ---> this takes around 5~10 seconds.

10-2. "fastboot flash dtbo dtbo.img" ---> this takes around 5~10 seconds.

10-3. "fastboot flash super super.img" ---> this takes several minutes.

11. After the steps above are complete, choose Enter recovery. After the phone enters recovery, choose Apply update->Apply from ADB

12. After choosing Apply from ADB, type "adb sideload <the path where you saved Google apps to>" on the Command Prompt and press enter.

13. After about 1-2 minutes, installation should be complete. Again, ADB might show "Failed to read command" errors. As long as the phone says that it was success, this is no problem. After installing, click on the "back" icon on the top of the phone.

14. Choose Factory reset->Format data/factory reset, and reboot the device.

15. If everything went well, the phone should reboot into Android 12 AOSP. Set up the device and Enjoy!

Changelogs:

2021-10-19: Initial Release (AOSP 12.0.0_r2)

2021-10-21: Updated to AOSP 12.0.0_r3

2021-11-03: Updated to AOSP 12.0.0_r13 & added U7 support

2021-11-22: Fixed graphics issue, fixed battery issue (when battery level sometimes dropped by more than 2-3% on reboot), and fixed force crash when choosing Battery Manager in Settings

2021-11-25: Updated to AOSP 12.0.0_r15, changed battery mechanism to make it more accurate

2021-11-27: Kernel GPU driver update (R33P0 -> R34P0), LTE is now enabled by default

2021-12-10: Updated to AOSP 12.0.0_r16, removed the annoying search box widget on the home screen

2022-01-01: EGL graphics driver update to improve performance, minor bug fixes related to some apps.

SCREENSHOTS:

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