Although rooting is no longer as big a thing compared to the earlier days of Android, installing custom recovery still has a ton of uses no Android app can provide.
To install TWRP, however, you do need an unlocked bootloader first, which is why this particular unofficial version of TWRP for the Galaxy S8 Snapdragon models is rather significant.
The bootloader situation with Samsung’s devices has always been complicated, especially with flagships that have two different processors.
Galaxy S8 and S8+ models using Samsung’s own Exynos processor are relatively easier to unlock, simply needing a toggle (OEM Unlock) to allow it and using tried and tested tools and methods.
The situation with the Snapdragon models is different and has a slight twist to it this year.
However, there are some, particularly those sold in China and Hong Kong, that seem to go against the flow and are easily unlocked.