Apache NuttX
7.3#4 in operating systemsFree planFree planAPILinuxmacOSSelf-hosted
VisitApache NuttX suits developers building software for embedded boards and devices, including projects spanning different processor architectures. Its documented simulator targets may also fit development workflows that do not rely solely on physical hardware.
PX5 RTOS is aimed at developers of embedded systems for safety-critical automotive, industrial, medical, rail, and other demanding applications. Its listed processor and developer-tool support can help teams check compatibility before evaluating it.