os: arch linux 6.10.6-zen1-1-zen
keyboard: unicomp pc-122 over ps/2 (custom xmodmap and setkeycodes script, system recognizes all keys properly and should not have any issues with interpreting the scancodes as proper keys)
version: 0.18.4-alpha.1 on minecraft 1.20.4
used with: litematica 0.17.3

upon attempting to use keys from f13 to f24 to set a hotkey, no input is registered at all. other keys work completely fine.

Do those keys work in vanilla hotkeys? Currently malilib doesn't use the scan codes, but rather the key codes for the hotkey system (which also causes issues like the shown keys only matching on the QWERTY layout).

I'd be interested to see the output if you enable the Debug -> keybindDebugging option (A + C to access the malilib config menu, or via the Mod Menu mod list) and then press those keys and look in the game console/log for the output.

For example here is the output I get for F9 - F12:

[19:29:53] [Render thread/INFO]: PRESS F9 (keyCode: 298, scanCode: 75, modifiers: 0), held keys: F9 (298)
[19:29:53] [Render thread/INFO]: RELEASE F9 (keyCode: 298, scanCode: 75, modifiers: 0), held keys: <none>
[19:29:53] [Render thread/INFO]: PRESS F10 (keyCode: 299, scanCode: 76, modifiers: 0), held keys: F10 (299)
[19:29:53] [Render thread/INFO]: RELEASE F10 (keyCode: 299, scanCode: 76, modifiers: 0), held keys: <none>
[19:29:54] [Render thread/INFO]: PRESS F11 (keyCode: 300, scanCode: 95, modifiers: 0), held keys: F11 (300)
[19:29:54] [Render thread/INFO]: RELEASE F11 (keyCode: 300, scanCode: 95, modifiers: 0), held keys: <none>
[19:29:57] [Render thread/INFO]: PRESS F12 (keyCode: 301, scanCode: 96, modifiers: 0), held keys: F12 (301)
[19:29:57] [Render thread/INFO]: RELEASE F12 (keyCode: 301, scanCode: 96, modifiers: 0), held keys: <none>