Cyberpunk 2077: Phantom Liberty introduces - among other big new features - a whopping new story for you to get involved in. However, if you're not feeling another great questline, you can end it super early.
There's a dialogue option that just allows V to walk away from the quest in Phantom Liberty. This will lock you out of furthering the mission, as the other characters will choose to go on without you. This is a great bit of attention to detail by CD Projekt Red, but we can't recommend this option if you've just bought the DLC.
In a roleplay sense, it does make some sense, as V might not necessarily want to get involved with anything that isn't directly related to getting Johnny Silverhand out of their head. As PC Gamer pointed out, you can do this in the fourth mission in Phantom Liberty, which is pretty early on.
Would you ditch the main questline in Phantom Liberty?