Need a workaround to downgrade back to Android 9 of lower bootloader Ver.

[alshab]

Hello,
I desperately want to downgrade my M30s (SM-M307FN) back to android 9.
It seems that i have no chances with the official firmware because my current bootloader is now ver 3 and there is no ver 3 android 9 firmware.
My current Software is :
PDA = M307FNXXU2BTD1
CSC = M307FNOJM2BTG1

What are my available options?
If I unlocked my bootloader and installed TWRP, would that allow me to use the official android 9 firmware and downgrade?
IF not?
Is there Any know stable Custom Roms that would bring me Android 9 and known to work smoothly on M30s?

I have no experience with custom ROMs, so I need directed ROMs recommendations if possible.
Please

[henklbr]

Hello,
I desperately want to downgrade my M30s (SM-M307FN) back to android 9.
It seems that i have no chances with the official firmware because my current bootloader is now ver 3 and there is no ver 3 android 9 firmware.
My current Software is :
PDA = M307FNXXU2BTD1
CSC = M307FNOJM2BTG1

What are my available options?
If I unlocked my bootloader and installed TWRP, would that allow me to use the official android 9 firmware and downgrade?
IF not?
Is there Any know stable Custom Roms that would bring me Android 9 and known to work smoothly on M30s?

I have no experience with custom ROMs, so I need directed ROMs recommendations if possible.
Please

Hi there

It's not possible to downgrade your device to Android 9 due to security...

Maybe a Samsung Service Point can help you.

We don't support TWRP & Custom ROM's; when using those, you'll lose the secure functions of your phone...

[alshab]

Thank you for your reply,
I don't think that a service point will do such a request.
But thank you again for you advice