
Samsung Galaxy Tab S9+, 12GB RAM +
Every official firmware build for SM-X810N, newest first: one row per build with all regions (CSC) that received it.

SM-X946B

SM-X846B

SM-X840

SM-X940

SM-X110N

SM-X350N

SM-X300N

SM-X210N
You can find the firmware on the model: SM-X810N page.
Yes, all firmware files for SM-X810N are 100% official, original, and obtained directly from Samsung servers.
To flash SM-X810N, 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-X810N.