Help : iMac 21.5-inch, Mid 2011 white screen (of death?) while booting

Hello everyone,

I have an old iMac 21.5-inch, Mid 2011

2.5 GHz Intel Core i5

8 Go 1333 MHz DDR3

AMD Radeon HD 6750M 512 Mo

macOS High Sierra 10.13.6

One day it just started booting with no boot sound and the loading bar

under not filling entirely before getting a white screen with nothing to do.

After some search on google I reset the mac PRAM NVRAM (with Option, Command, P, and R)

which restored the mac booting sound but nothing else. Tried to reset

the SMC but I have no idea if I've done it correctly or not

I tried booting into :

- Safe mode (holding shift) : white screen

- Recovery (command, R) : white screen

- Internet recovery (command, option, R) : Show the globe and loading bar gets to white screen before the end

- Hardware scan (D) : Boot fine into it, no problem detected by the scan

- Startup manager (Option) : Can choose between the main partition and the recovery : White screen on both

- Single User Mode (Command, S) : Boot fine into, tried the repair disk command (/sbin/fsck -fy) repaired something but didn't change the white screen problem

Now I tried creating macos recovery/install boot disk but since I don't

have any other mac it was an ordeal, some USB weren't recognized some

were but none got past white screen.

After that I made a Linux Mint live USB with Ventoy which I can boot

into if I select GRUB2 mode then compatibility mode in the choices.

Linux Mint seems to run pretty fine with no problem whatsoever (I'm

currently using this method to recover important files on the HD).

I found a thread (don't remember where) which had really

similar symptoms, that talked about dead (or malfunctioning) GPU and that a

solution might have to be to force booting with the internal GPU but I

found after that the thread were about macbooks and not iMac, I also

read somewhere that those iMac absolutely not use integrated graphics I

found other threads that say they do so I'm lost and I don't know who to

trust.

Now with all this information what do you think I can do ?

Is there a way to recover/reinstall a macOS on this machine or should I

(after recovering all important file) install another OS on it ?

I appreciate your help in advance,

LDG