I observed some questions on the Internet concerning this.

* [F20-F24 keys do not respond, but are mapped](https://apple.stackexchange.com/questions/192066/f20-f24-keys-do-not-respond-but-are-mapped)
* <https://forum.keyboardmaestro.com/t/f-keys-f13-to-f24/8953>
* <https://discussions.apple.com/thread/1090226>

Karabiner-Elements can map from F1~F24, but can only map to F1~F20

And you can tell the OS is aware of there keys from this reply: <https://forum.keyboardmaestro.com/t/f-keys-f13-to-f24/8953/7>

So what's peculiar about F21~F24 on MacOS?