I've worked with QNX for years and wrote a clone, this is an amazing little OS that you can build rock solid services on. It's a pity that there never was much interest in something along these lines but open source.
Do you have a link to your version? How compatible was it?
I seem to remember eagerly grabbing a copy from Github around 2010-2011, but unfortunately that was on a work laptop from a previous job.
In my experience Linux has been pretty awful at this.
isn't the problem these days just crappy random hardware more than anything else; Linux itself, especially with rt patches, together with jack should have good enough rt perf for audio use. I've seen reports of <5ms roundtrip audio latency on linux even with usb hardware.
Could be wrong, but I think it has been default on Ubuntu Studio and alike for at least a year now.