Samsung Galaxy A20s

Device

Summary of what works and doesn't

Make sure you have a way to revert back to stock firmware if needed (this usually goes without saying).
Make sure to unlock your A20s bootloader, won't tell you how since it's easy af
Download a GSI, and make sure it's ARM64 A/B vndklite
- You may also download Gapps GSIs if you want, but I don't know if the system partition on this device will allow for this.
- The maximum size for a GSI as I tested was 2.3GB, others larger may or may not work, haven't tested.
Download heimdall-flash package, if you are on fedora (which I recommend), you can just do that:

sudo dnf install heimdall

Prepare your GSI by storing it alongwith an empty vbmeta (to disable secure boot verification) in a folder, let's say the folder will be called a20s_gsi, you may create that folder in your home directory by running the following commands:

cd ~
mkdir a20s_gsi
cd a20s_gsi

Copy your GSI file into that folder, you may just use the graphical file manager to simplify that process, and rename it gsi.img
Copy the empty vbmeta image file avbnull.img file into the same folder as above (you may download this file from here if you don't have it)
Fully power down your phone (long press power button and tap "power off" twice, then wait for screen to be fully dim and for the device to viberate).
Reboot into recovery mode, and do a factory reset and erase cache partition, then choose power off
Boot into download mode (long press both volume buttons then connect usb cable then let go of all buttons when the screen turns on)
Press volume up once to confirm going into DL mode
Connect your phone into your pc and run

heimdall detect

this should give device detected.

Start a terminal in the same directory you created earlier in this guide (in this case it's the a20s_gsi folder) and run the following commands:

heimdall flash --SYSTEM gsi.img --VBMETA avbnull.img

where of course gsi.img should be the gsi file
and avbnull.img is the empty vbmeta image file
Press enter, wait for it to reach 100% for both SYSTEM and VBMETA, once completed, your phone will reboot, enjoy!

Component	Comment
Camera	Works
Speaker / Mic	Works
Bluetooth	Works (and BT Audio works too)
WiFi	Works
SIM / Mobile Data / Voice	Works (To hear others in call you have to enable some option in Phh Settings>Misc settings under telephony settings)
VoLTE	Not working, works in stock FW
Fingerprint	Works
Offline Charging	Untested
Fast Charging	Works
Screen mirroring (Cast)	Doesn't work
SD Card	Works
MTP (Connection to PC via Cable) and other connection modes	Doesn't work
ADB via USB and WiFi	Works
Other feature	To be tested

Tested By: InsertX2k - On SM-A207F/DS(EGY), Build Number - A207FXXS5CWF1

GSI Tested: LineageOS 20.0 TD-Based (arm64 a/b vndklite GSI)

This device booted properly on Android 14 TrebleDroid GSI

Component	Comment
Camera	Works
Speaker / Mic	Works
Bluetooth	Works (and BT Audio works too)
WiFi	Works
SIM / Mobile Data / Voice	untested
VoLTE	Not working, works in stock FW
Fingerprint	Works
Offline Charging	Untested
Fast Charging	Works
Screen mirroring (Cast)	Doesn't work
SD Card	Works
MTP (Connection to PC via Cable) and other connection modes	Doesn't work
ADB via USB and WiFi	Works
Other feature	To be tested

Unfortunately, not booting in Android 15 TrebleDroid GSI, this may get fixed in later updates of TD GSIs, but that's what I tested.

End