For those of you with Korean Galaxy S5 such as SM-G900S, SM-G900K, and SM-G900L, there is now a way to install custom ROMs on your Korean Galaxy S5. You should be able to install any SM-G900F or T-Mobile SM-G900T custom ROMs like Alliance ROM easily.
This method basically uses enable Carrier WiFi, CSC, and boot image, which is disabled on Korean Gaalxy S5 by default.
Basically, you need to flash the enable zip file after installing your desired custom ROM. For installation of custom ROMs, see How to Install Custom ROM on Galaxy S5!
You can download Enabler zip here: