How can I set up cross progression in 2025?

To play the game you are required to have your platform account linked to an EA Account, it would not have been possible to have played the game without having done so; this was also the case a long time ago.

So it's granted that your PSN Account was linked to an EA Account when you were playing a while back. What I've noticed that this usually goes by unnoticed by a lot of console players, as in some cases a new EA Account is simply created when trying to play the game. (I'm not well versed with this process as I don't own a console, but I hear quite often from users on consoles that they aren't aware that their account is linked to an EA Account) So yeah it's like you're saying, seems like they created it automatically.

The thing is, your account progress would be stored on that EA Account. You'll need to get access to that EA Account, either by getting your relative to give you the code so you can move your EA Account to a different email, or by getting EA Support to assist you with it.

Because the data is stored on the EA Account, it wouldn't matter if you were to relink your PSN Account.
Platform accounts only get access to the data from the EA Account they are linked to, so re-linking would result in your PSN Account getting access to the data of a different EA Account, and thus not have the original progress that you made before via PlayStation.