alt Hacker NewsLinux (well, more accurately, X11), has had a SAK for ages now, in the form of the CTRL+ALT+BACKSPACE that immediately kills X11, booting you back to the login screen.
I personally doubt SAK/SAS is a good security measure anyways. If you've got untrusted programs running on your machine, you're probably already pwn'd.
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The "threat model" (if anyone even called it that) of applications back then was bugs resulting in unintended spin-locks, and the user not realizing they're critically short on RAM or disk space.
This setup came from the era of Windows running basically everything as administrator or something close to it.
The whole windows ecosystem had us trained to right click on any Windows 9X/XP program that wasn’t working right and “run as administrator” to get it to work in Vista/7.
That's not a SAK, you can disable it with setxkbmap. A SAK is on purpose impossible to disable, and it exists on Linux: Alt+SysRq+K.
Unfortunately it doesn't take any display server into consideration, both X11 and Wayland will just get killed.