Yes, unless the family immigrates, it is not possible to sign non-EU- U18 players.
But we should be able to negotiate with the club and the player for a future transfer, like the case of Endrick, but I also noticed an increased reluctance in the U18 newgew's (or real players) wanting to join the club a Top Tier club. Even in the club accepts the fee most of the times players don't want to sign.
It's definitely different than in past FM's, but it's okish for me, as I also liked to hunt and bring newgen diamonds to my club.