Samsung uses "Download Mode" instead of standard Fastboot. This Termux method is generally not compatible with Samsung's proprietary Odin protocol. Final Security Warning
October 26, 2023 Subject: Feasibility and Methodology of Unlocking Android Bootloaders via Local Terminal Emulation Target Audience: Security Researchers, Android Developers, Advanced Users unlock bootloader via termux
Unlocking a device bootloader via Termux is possible on some Android devices but is generally complex, device-specific, and risky. Termux can provide a convenient Linux-like environment on-device, but it has limitations compared with using a PC and official fastboot/adb toolchains. Choose this route only if you understand the risks and your device’s exact unlocking procedure. Samsung uses "Download Mode" instead of standard Fastboot