The PREEMPT_RT patches (aka “Real-Time Linux”) originated as a set of out-of-tree mods to the Linux kernel about 20 years ago. Bit by bit, over time, various parts of them have been incorporated into the mainline code. Some of these patches have found uses in, shall we say, more mainstream application areas. And beginning with kernel version 6.12, the last of those out-of-tree patches have been merged, and the out-of-tree PREEMPT_RT patchset is no more. This article <https://www.zdnet.com/article/20-years-later-real-time-linux-makes-it-to-the-kernel-really/> by long-time Linux fan Steven J Vaughan-Nichols, gives some background. Including the fact that musicians have been using Linux for audio work for decades, because Linux with the real-time patches was the cheapest way of recording pro-quality audio, much cheaper than buying “real” pro audio gear.