
Samsung Galaxy Tab S2 9.7
Every official firmware build for SM-T815N0, 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/T815N0KOS2CTJ3
Specifications of SM-T815N, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.

SM-T815Y

SM-T810X

SM-T818V

SM-T800X

SM-T820X
You can find the firmware on the model: SM-T815N0 page.
Yes, all firmware files for SM-T815N0 are 100% official, original, and obtained directly from Samsung servers.
To flash SM-T815N0, 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-T815N0.