
Samsung Galaxy A8+(2018)
Every official firmware build for SM-A730X, newest first: one row per build with all regions (CSC) that received it.
Specifications of SM-A730F, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.

SM-A730F

SM-A736B

SM-A725M

SM-A720S

SM-A530X
You can find the firmware on the model: SM-A730X page.
Yes, all firmware files for SM-A730X are 100% official, original, and obtained directly from Samsung servers.
To flash SM-A730X, you need to download the appropriate firmware, put your device into Download Mode, and use the Odin tool to load the BL, AP, CP, and CSC files.
Downgrading is only possible if the bootloader version (binary bit) of the old firmware matches the current one. Always check the binary version before flashing SM-A730X.