
Samsung Galaxy S5 mini
The latest firmware for Samsung Galaxy S5 mini (SM-G800M) is G800MUBS1CRL9 with Android 5.1.1 (Marshmallow), released on December 18, 2018 for 5 regions (CSC). Every official firmware build for SM-G800M, 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/G800MUBS1CRL9
SM-G800M started on Android 4 and has received 1 major Android upgrade; it now runs Android 5.1.1 (Marshmallow). The newest build, G800MUBS1CRL9, was released on December 18, 2018. No new build has appeared for 95 months, so regular updates for this model have most likely ended.
Specifications of SM-G800F, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.

SM-G800X

SM-G900AZ

SM-G9098

SM-G903W

SM-G901F
The newest firmware for SM-G800M runs Android 5.1.1 (Marshmallow): build G800MUBS1CRL9, released on December 18, 2018.
The latest build for SM-G800M, G800MUBS1CRL9, was released on December 18, 2018 (7 years ago).
SM-G800M has had no new firmware for 95 months, so regular updates have most likely ended.
Yes, all firmware files for SM-G800M are 100% official, original, and obtained directly from Samsung servers.
To flash SM-G800M, 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-G800M.