It's barely usable when paired with the Realtime patchset. An actual OS that constitutes a "good audio stack" would be able to provide hard realtime (i.e. form

It's barely usable when paired with the Realtime patchset. An actual OS that constitutes a "good audio stack" would be able to provide hard realtime (i.e. formally guaranteed maximum latencies), like seL4 does. Linux-rt is just probabilistic. It behaves much better than mainline, but latency could spike anytime.