
Samsung Gear S (Wi-Fi/Bluetooth)
The latest firmware for Samsung Gear S (Wi-Fi/Bluetooth) (SM-R750J) is R750JKDU1APA4 with Android 2.2.1.3, released on January 11, 2016 for 1 region (CSC). Every official firmware build for SM-R750J, 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/R750JKDU1APA4
All 5 builds in our database run Android 2.2.1.3. The newest build, R750JKDU1APA4, was released on January 11, 2016. No new build has appeared for 131 months, so regular updates for this model have most likely ended.
Specifications of SM-R750, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.

SM-R750D

SM-R850N

SM-R765N

SM-R855F

SM-R640N
The newest firmware for SM-R750J runs Android 2.2.1.3: build R750JKDU1APA4, released on January 11, 2016.
The latest build for SM-R750J, R750JKDU1APA4, was released on January 11, 2016 (10 years ago).
SM-R750J has had no new firmware for 131 months, so regular updates have most likely ended.
Yes, all firmware files for SM-R750J are 100% official, original, and obtained directly from Samsung servers.
To flash SM-R750J, 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-R750J.