
Samsung Galaxy J6
The latest firmware for Samsung Galaxy J6 (SM-J600N) is J600NKOS5CUL1 with Android 10, released on December 22, 2021 for 1 region (CSC). Every official firmware build for SM-J600N, newest first: one row per build with all regions (CSC) that received it.
Each firmware build has its own page at https://samfirm.shop/build/{PDA}, where {PDA} is the build number from the list above. Example: https://samfirm.shop/build/J600NKOS5CUL1
SM-J600N started on Android 8 and has received 2 major Android upgrades; it now runs Android 10. The newest build, J600NKOS5CUL1, was released on December 22, 2021. No new build has appeared for 59 months, so regular updates for this model have most likely ended.
Specifications of SM-J600F, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.

SM-J600L

SM-J700T1

SM-J500Y

SM-J701MT

SM-J610G
The newest firmware for SM-J600N runs Android 10: build J600NKOS5CUL1, released on December 22, 2021.
The latest build for SM-J600N, J600NKOS5CUL1, was released on December 22, 2021 (4 years ago).
SM-J600N has had no new firmware for 59 months, so regular updates have most likely ended.
Yes, all firmware files for SM-J600N are 100% official, original, and obtained directly from Samsung servers.
To flash SM-J600N, 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-J600N.