From going through the discussion I'm getting the impression that the only feasible attack vector provided by USB is by emulating a keyboard like a USB Rubber Ducky. Is this really the case?

For instance, if my laptop is locked (with a proper[0][1] lock screen like xscreensaver) and that lock screen is capturing all keyboard input and magic SysRq keys[2] are disabled, too, is there really no way an attacker could use a USB device to hack my laptop?

Similarly, if my laptop is not locked but comes with unusual key bindings (maybe even a different keyboard layout), what are the chances of me getting hacked with a USB device? (Let's assume that the attacker manages to secretly plug in said USB device but doesn't want to access my unlocked laptop directly – maybe because we're in an open office and people are watching.)

My impression had always been that USB devices are dangerous beyond simple keyboard emulation but I might be wrong.

[0] https://www.jwz.org/blog/2015/04/i-told-you-so-again/

[1] https://www.jwz.org/xscreensaver/toolkits.html

[2] https://en.wikipedia.org/wiki/Magic_SysRq_key