In Red Dead Redemption 2 there are 19 Shack locations. You only need 5 of the shacks to bring the game progress to 100%. You can look up this task in the menu under Game Progress and Misc.
All but two you can visit once you’ve reached chapter 2 in the story. In the huts you will also find useful prey and cigarette images. The two huts that are not yet available in Chapter 2 will appear after the story ends.
There are more shacks than you need for the game progress, below you will find 5 huts sites in the video.