
Samsung Galaxy TabS 8.4
The latest firmware for Samsung Galaxy TabS 8.4 (SM-T705M) is T705MUBS1CSA1 with Android 6.0.1 (KitKat), released on January 29, 2019 for 1 region (CSC). Every official firmware build for SM-T705M, 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/T705MUBS1CSA1
SM-T705M started on Android 4 and has received 2 major Android upgrades; it now runs Android 6.0.1 (KitKat). The newest build, T705MUBS1CSA1, was released on January 29, 2019. No new build has appeared for 94 months, so regular updates for this model have most likely ended.
Specifications of SM-T705, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.

SM-T705Y

SM-T800X

SM-T710X

SM-T719C

SM-T727A
The newest firmware for SM-T705M runs Android 6.0.1 (KitKat): build T705MUBS1CSA1, released on January 29, 2019.
The latest build for SM-T705M, T705MUBS1CSA1, was released on January 29, 2019 (7 years ago).
SM-T705M has had no new firmware for 94 months, so regular updates have most likely ended.
Yes, all firmware files for SM-T705M are 100% official, original, and obtained directly from Samsung servers.
To flash SM-T705M, 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-T705M.