[General Questions and Answers] OldNoobOne:
1) Hi Radikyrick, Actually i'm just a disillusioned user so all thanks should go to XDA & Galaxy M21 t.me group coz thats where i had found bootlogo patch zip, Multi-disabler zip etc., they were quite supportive group. Also, thanks to dev GuruPrasadAH for GSI-flashing easy method.

2) Unfortunately, M215G is still a new model (NOT coz it is identical to M215F on specs but more bcoz it runs on Andoid 11) so installing heimdall is just one part but its too early for a Final Build ROM as the devs are probably still working on a ROM for M215G (They might not have given up on M215F or M215G just yet)

3) Look, If you have anything to hide then I dont think netguard or any other firewall would be able to fully stop system apps from unauthorized access to satellites, the reason I say this is bcoz if netguard or any firewall really tries to prevent system apps to connect to satellites then THE DEVICE SHOULD HEAT UP & BATTERY SHOULD DRAIN FASTER! but that isnt the case coz neither battery drain happens much nor does the device heat up (as the system apps would continuously try to access the satellites to pass user data to gugle & OEM servers). Moreover the Artificial Intelligence built in andoid probably already takes into account that the user might be installing a firewall app, so system apps still could be using built-in AI to bypass firewalls without the user or firewall app knowing about the breach. That is a possibility. At the most i'd say Firewall apps can be usefull to prevent 3rd party apps from accessing satellites.

4) Debloat list is an old thing but I have had some success with regards to Fused Location 11 app but it still cant be blocked probably bcoz Andoid 11 doesnt give user permission to do that.

[Besides, andoid 11 onwards gugle prevents users to hide their locations so it is keeping Terrorism-Tracking above a users personal rights to privacy!, as in my case, before pandemic I had borrowed a large sum of money from some shady money-lenders who use andoid to track their borrowers and these characters happen to be more of instinctual bonecrushers than accomodative bizness people, so if I dont pay up on time then they can come to my doorstep to use force and no one can drag gugle to court for allowing such characters to use gugle services to track their defaulters as these people dont use gugle officially for tracking their defaulters but seem to use gugle employees to do the tracking job for them (my logical conclusion), how else can they come to know someones exact locations?]

5) Steps to Unlock Bootloader -

Unlock your phone and open the Settings menu.

Scroll down and tap on About Phone -> Software Information.

Find Build Number. Quickly tap seven times. This will enable Developer Options.

Go back to the Settings menu, scroll down and tap on Developer Options.

There is a toggle called OEM Unlocking: Allow the bootloader to be unlocked. Tap on the toggle.

Now press and hold the power button. Tap on Power off to turn off the phone.

Hold the volume up and volume down buttons while connecting your phone to a computer via a USB cable. The phone will boot into Download Mode.

The phone will show a Warning screen. Press and hold the volume up button one more time.

The phone will show an Unlock Bootloader? screen. Press and hold the volume up button. This will unlock the bootloader and all data on your phone will be deleted.

The phone will automatically reboot. Connect your phone to a WiFi network and skip through the rest of the setup.

Go to Settings > About Phone > Software Information and quickly tap 7 times on Build Number to enable Developer Options. Go to Developer options and make sure that OEM unlocking is greyed out.

This will unlock the bootloader of your Samsung Galaxy M21 2021 Edition. Once the bootloader is unlocked, all data on your phone will be deleted. The phone will revert to stock factory settings.

6)

Steps to Flash GSI (M215G)-

a) Download and Run latest ODIN on PC.

b) Connect device to PC using USB Cable.

c) Press Vol Down + Power button to enter Download Mode.

d) Load Soulr344 TWRP Tar file on AP-section of ODIN, keep Auto-Reboot &

F.Reset Time options Unchecked under Options tab.

e) Click Start button in ODIN.

f) Press Power + Vol Down button for 3-4 seconds, after screen blacks out,

Press Power + Vol Up button till you see TWRP screen.

g) Inside TWRP, tap on check-box and slide scroll bar to Allow Modifications

then tap on MOUNT tab then select all options that can be selected. Also,

Enable MTP button if Disabled.

h) Remove USB cable (follow USB removal procedure) then transfer Muti-

Disabler zip to any USB-PenDrive & attach that Pen-Drive to M215G

device (Use Type-C Adapter), Select USB-OTG option in TWRP MOUNT tab

then flash Multi-Disabler zip using the INSTALL tab in TWRP.

i) In TWRP tap on WIPE tab , select Dalvik/ART Cache & Data partition then

swipe to wipe.

j) In TWRP tap on REBOOT tab, reboot to Recovery then after reboot in

MOUNT section select all partitions.

k) Uncheck USB-OTG option in TWRP MOUNT tab & remove Pen-Drive.

l) Re-Connect M215G Device to PC using USB cable.

m) On PC open new Win-explorer window, double-click M215G Device name,

then double-click on Internal Storage, then double-click on Document

Folder.

n) Transfer GSI img file , Bootlogo Patcher zip, Multi-disabler zip, Overlay Fix zip,

vbmeta zip, Prish Kernel Zip, latest magisk zip etc. to Document folder inside

Internal Storage.

o) Remove USB cable (follow USB removal procedure).

p) In TWRP, tap on ADVANCED tab, then tap on FILE EXPLORER tab, then tap on

SDCARD tab, then tap on Document tab and check if all transferred files are

present there. Press back button in TWRP navigation panel till you come back

to ADVANCED tab.

q) In TWRP, tap on ADVANCED tab then tap on TERMINAL tab.

r) In TERMINAL console -

Type the following commands one by one :

1> cd sdcard

2> cd documents (case sensitive so check if name of folder is document/

Document/ Documents/ documents)

3> super mount system

4> super flash system [Name-of-the-GSI-image].img

s) Wait for TERMINAL Console to flash the GSI-image (about 10 seconds)

t) Press back button in TWRP navigation panel till you reach main TWRP screen.

u) In TWRP main screen, Tap on INSTALL tab then Flash - vbmeta zip,

multidisabler zip, magisk zip, Prish Kernel zip, Overlay Fix zip etc.

v) Press back button in TWRP navigation panel till you come to main screen,

then tap on REBOOT tab , tap on Recovery , Once device reboots to TWRP

Recovery, Tap on Mount tab, then select system partition and all other

partitions, then press back button to go to REBOOT tab, then tap on System.

Device should boot to GSI image.

w) If you dont like the GSI image, then tinker around settings options or phh-

treble settings options and try to customize it as much as possible. (some

trade-offs have to be done coz device-specific advanced drivers are typically

missing in GSI images but it is basic functional system image, so try to

update the device over internet if it helps)

x) If still not happy, then drain the device battery using battery waster app then

repack the device in its original package box , then keep inside moistureless

dry dark corner of cupboard AND FORGET ABOUT DEVICE FOR AT LEAST 6

MONTHS TO 1 YEAR then CHECK BACK IN XDA FORUM FOR

OFFICIAL/UNOFFICIAL ROMs.

y) If after one year you still didnt find proper ROM for the device then sell off

the device at a loss, contact your Accounting Firm, tell them to add device

name & amount to Depreciation Account which will show up under Profit &

Loss Account eventually in Balance Sheet so as to pay less tax for the amount

you lost.

Thanks :D