Mayhem can test standalone C/C++ targets compiled without any instrumentation, and targets compiled with AFL / AFL++, Honggfuzz and LibFuzzer.
Mayhem has an ability to auto-detect native Golang targets and set an environment variable in the Mayhemfile which instructs the Mayhem on how to handle Golang exceptions.
Mayhem can test standalone Rust targets compiled without any instrumentation, and targets compiled with AFL and CargoFuzz.
Mayhem can fuzz the following Java targets: Base-Executable and LibFuzzer (Jazzer).
Mayhem can fuzz Python targets in LibFuzzer (Artheis).
Mayhem can fuzz Ada Base-Executables.
Although not a specific language, Mayhem works with your firmware RTOS.