If you buy the PS5 Disc, there's a code in the box that's meant to give you the DLC for the game.

Do PS5 disc games come with digital code?

No, you would just receive one copy of Watch Dogs Legion for PS5.

Do Playstation discs come with digital copy?

No, If you have a digital console and buy a game on disc you will have just wasted your money. If you got a code everyone would just buy a game and immediately sell the disc to recoup the costs and essentially have a free/heavily discounted digital game.