The Last of Us Part II Remastered features three lost levels. To see how you can access these unfinished stages, you can take a look at this tutorial from Seeking Tech.
1. To start off, make sure you are in the main menu of the game.
2. From there, select the “Making Of” option.
3. In the “Making Of” menu, select Lost Levels.
4. On the next screen, you should see the Jackson Party, Seattle Sewers and The Hunt levels.
On the right of the screen, you should see a short description of the stage along with a warning text saying that it is in a pre-alpha state. For the Jackson Party level, there is also additional text explaining that it does not have spoken dialogue.
5. Once you pick a level, you will be taken to a new screen.
Here, you can choose whether or not you want to enable developer commentary or the introduction video.
When you are ready, select the Start option to start playing the lost level.