A firmware for the "Samsung S4 i9500" will brick an "i9505." Be exact.
While most modern apps require Android 10 or higher, KitKat is still useful for:
Using old hardware as a dedicated smart home controller or digital clock. Popular Types of KitKat Firmware
Usually Odin (for Samsung), SP Flash Tool (for MediaTek), or ADB/Fastboot (for Pixel/Nexus). Backup: Flashing a new firmware will wipe your data. Conclusion