I have a special keyboard that can produces keycodes for F21-F24. The SDL2 seems not to hadle it, with the following messages:
The key you just pressed is not recognized by SDL. To help get this fixed, please report this to the SDL forums/mailing list <https://discourse.libsdl.org/> X11 KeyCode 199 (191), X11 KeySym 0xFFD2 (F21).
Can’t it be supported somehow?