Here is Havoc os 4.1 for Samsung galaxy m21
Make sure your device is unlocked bootloader and installed latest twrp also be on latest firmware. Make sure you have stock firmware in your pc if something goes wrong you can flash stock rom by odin. Also do a backup of your all data.
I will not responsible for anything.
Highly customized stable fast android 11 gsi
Havoc os 4.1 gsi download
-MTP (you can use twrp mtp for transfering files)
-VOLTE (if your operator support 2g network you can still receive and make calls example airtel for India also 4g internet work without any problem)
-HOTSPOT (you can use usb tethering to share internet for pc but hotspot is a bug)
How to root?
Screenshots click on spoiler to see screenshots
@Nazim navas for zipping and upoloading Havoc os
@soulr344 for making gsi flasher zip and twrp
@ anurup jha for screenshots
@Sagarking me for writing thread
@Havoc team for awessome havoc gsi 4.1
and all other who deserve creadits but not mentioned