
Samsung Galaxy Tab S2 9.7
The latest firmware for Samsung Galaxy Tab S2 9.7 (SM-T817R4) is T817R4TYU1CQI5 with Android 7.0 (Nougat), released on September 21, 2017 for 1 region (CSC). Every official firmware build for SM-T817R4, 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/T817R4TYU1CQI5
SM-T817R4 started on Android 5 and has received 2 major Android upgrades; it now runs Android 7.0 (Nougat). The newest build, T817R4TYU1CQI5, was released on September 21, 2017. No new build has appeared for 110 months, so regular updates for this model have most likely ended.
Specifications of SM-T817T, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.

SM-T290N

SM-T537A

SM-T800X

SM-T807V

SM-T230X

SM-T230NY

SM-T237V

SM-T232
The newest firmware for SM-T817R4 runs Android 7.0 (Nougat): build T817R4TYU1CQI5, released on September 21, 2017.
The latest build for SM-T817R4, T817R4TYU1CQI5, was released on September 21, 2017 (9 years ago).
SM-T817R4 has had no new firmware for 110 months, so regular updates have most likely ended.
Yes, all firmware files for SM-T817R4 are 100% official, original, and obtained directly from Samsung servers.
To flash SM-T817R4, 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-T817R4.