Uninstall your Origin // EA, because the new patch from EA broke everything again, such a surprise...
*hum-hum*

Download the Origin Offline Installer by following this link :

• https://www.dropbox.com/s/o7auc5k5zmiudde/OriginSetup.exe?dl=1 

Install it, be sure to remove the checkboxes about "auto update"   ►

  After installation, DO NOT log in to your account yet  

Go to "C:\ProgramData\Origin" and open the file "local.xml" with any text editor like Notepad.
Before the last line </Settings>, add the following line (you will most likely need to add an empty line by pressing Enter first) :

• <Setting key="MigrationDisabled" type="1" value="true"/>

  Some applications "hide" essential files in folders that are hidden by default. To view the "ProgramData" folder, you will need to go to the Windows control panel , select "Appearance and Personalization", and find the "folder options" dialog.

Delete the files called "OriginThinSetupInternal.exe" which can be located at :

• C:\Program Files (x86)\Origin
  
• C:\ProgramData\Origin
  
• C:\ProgramData\Origin\SelfUpdate\Staged

It's also likely that when you run the game, Steam will try to install EA App .
To fix this, go into your game folder in "SteamLibrary\steamapps\common\Mass Effect Legendary Edition\__Installer\Origin\redist\internal", then delete the file "EAappInstaller.exe".

Also, open "SteamLibrary\steamapps\common\Mass Effect Legendary Edition\InstallScript.vdf" with Notepad, find "EAappinstaller.exe" and modify the following from "true" to "false". Now the game will start without that stupid popup which ask permission to install something.

Finally, log into your Origin account, everything should work fine !

  There may be an update notification on Origin window, just don't click on it (you can close it by clicking on the cross).

You can now enjoy getting your deserved rewards for saving the galaxy :)

Come here, gimme an high five.

► 30 May 2023 : Yes !

It doesnt work for me !

► Retry from the start and focus on every steps.

Maybe I should use comments methods ?

► Honestly, it mostly seems to doesn't work.
This guide does, once for all. Save your time.

Are the achievements retroactive ?

► Sadly not, you will have to play again to obtain your rewards.