Samsung Galaxy S7 Active
The latest firmware for Samsung Galaxy S7 Active (SM-G891A) is G891AUCU6CTB1, released on February 12, 2020 for 1 region (CSC). Every official firmware build for SM-G891A, 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/G891AUCU6CTB1
The newest build, G891AUCU6CTB1, was released on February 12, 2020. No new build has appeared for 81 months, so regular updates for this model have most likely ended.

SM-G935TZK

SM-G930AZK

SM-G935AZS

SM-G935TZS

SM-G935AZK

SM-G935TZD

SM-G975WC

SM-G975FC
The latest build for SM-G891A, G891AUCU6CTB1, was released on February 12, 2020 (6 years ago).
SM-G891A has had no new firmware for 81 months, so regular updates have most likely ended.
Yes, all firmware files for SM-G891A are 100% official, original, and obtained directly from Samsung servers.
To flash SM-G891A, 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-G891A.