Despite all having the name "Samsung Galaxy S8," there are in fact dozens of different variants of Samsung's flagship phone. But all the S8 devices worldwide have one of two processors - the Qualcomm 835, or the Exynos 8895. TWRP for the Exynos models arrived in April, but now it's time for the Snapdragon variants.
Now before all of you get excited, you still need to have an unlocked bootloader for this to work. Since no one has figured out how to unlock the US S8's bootloader, this will only work with the Chinese or Hong Kong variants (which have unlockable bootloaders and Snapdragon chips). If you were hoping to use TWRP with your 'Murican S8, you're out of luck for now.
But if you do have an unlocked Snapdragon S8, you can grab TWRP for it at the source link below.