Important info to remember when Debranding a Samsung devices.
What Chipset is the device on Exynos or Qualcomm
Whats is the device Model number example SM-J727A
What is the deivce build number? Note: you can only flash device with a firmware that is equal to or greater then the build the device is currently on now.
DeBranding a device will not carrier unlock it. Example if you flash the J727U unlocked firmware to the device it will still be Sim locked to the carrier IE ATT T-mobile and so on.
Noramlly you want to flash the U firmware to DeBrand the device. The U1 for US S8 or Note 8 and above devices. If you have a Exynos device then the unlocked firmware is normally the F firmware. example SM-G965F