Do you have to subscribe to playstation pluss to play battlefield 2042

In order to participate in multiplayer, yes

The game is online only so yes, any of the modes in BF2042 will require a PS+ subscription.  ....Portal, solo/coop, AOW and Hazard Zone.  If you don't plan on getting PS+ or cancelling it, I would not suggest buying the game.  It will be worthless otherwise.