The safest source for an authentic is the OpenTX GitHub repository.
To actually flash 2.1.9 to your radio, you need , not the modern Companion 2.3.
This version was primarily a maintenance and bug-fix release designed to improve stability and refine the telemetry system, which underwent a major overhaul in the 2.1 branch. It is still used today by hobbyists with legacy hardware who prefer the stability of this specific version over the more resource-heavy 2.2 or 2.3 releases. Key Features and Fixes
For older hardware, 2.1.9 is bug-free and less demanding on the processor than modern branches. Telemetry:

