Yep, that was it. Thanks for the reminder.

It works great for me on Arch with Hyprland, even though that really isn’t designed with touch in mind. I think there are some programs that provide touch gestures generically (egg something comes to mind?), but I’ve never needed them. I’m sure if you go with Gnome or something it would work great, so long as the touchscreen is recognised properly (I’ve never had issues, but that doesn’t say much about if you would). I’d just get a live USB with whatever you would install, and see if it physically works. If it does, I’m sure there’s a DE/WM that fits the workflow you want.

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.