RT Linux is not the only alternative. There are now plenty of options for achieving hard real-time performance without relying on proprietary RTOS solutions:

  Dedicated Real-Time Cores: Many SoCs include dedicated cores specifically for hard real-time tasks.
  Microcontroller Companions: Pairing a microcontroller running a lightweight RTOS with a larger, general-purpose processor as a supervisor (You can use normal Linux).
  FPGAs: Custom FPGA implementations can deliver deterministic timing where ultra-low latency or specialized processing is needed.

Is there a good libre real-time OS you would recommend over it?

Agree but I have seen more people wrongly think they need hard real time than people incorrectly picking their kernel.

I don’t doubt this but it’s worth noting that I believe spacex uses Linux as their RTOS.

talk nerdy to me, which ones ?

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