I’m looking to create a macro keyboard (full keyboard) which is separate from my main keyboard, under Debian with KDE Plasma running under Wayland. I have seen similar tools for X11 but they do not work under Wayland for obvious reasons. I have been able to create basic macros using Python, but is there a much better way for Wayland?
You could do that at the firmware level, with QMK or ZMK macros (or, presumably, whatever other firmware). It might be a long one, but launching an application or the like could just be typing the combination that runs it. I haven’t used KDE, but something like super, then type the name, then enter, should work.
Having said that, a quick look at keyd proposed by the other replier does seem like it has more than enough capability, and if you have one setup you want to use it for and not move the keyboard between computers, it very well might be the better choice for you.