Do not panic. Download the correct firmware, remove the battery and USB cable, then use a physical DFU jumper (on very old radios) or try the "unbrick" procedure using dfu-util -a 0 --unlink .
Before diving into the specifics of version 2.1.9, it is essential to understand the significance of the OpenTX project. OpenTX is open-source firmware for RC transmitters. It replaced the proprietary, often limited firmware found on radios from manufacturers like FrSky (Taranis series) and FlySky. opentx 2.1.9 download
The internet is filled with sketchy file repositories. You risk bricking your radio with corrupt or malicious binaries. Do not panic