So, it looks like i've got a more-or-less functional touchscreen (maybe i'll have some questions later about ironing out details). but i can't seem to get a virtual keyboard working. i've allegedly installed qt5-virtualkeyboard w/ pacman, but I'm not sure I understand pacman properly, becasue this output doesn't make sense to me:

ezpad  ~  sudo pacman -S qt5-virtualkeyboard
warning: qt5-virtualkeyboard-5.13.0-1 is up to date -- reinstalling
resolving dependencies...
looking for conflicting packages...

Package (1)               Old Version  New Version  Net Change

main/qt5-virtualkeyboard  5.13.0-1     5.13.0-1       0.00 MiB

Total Installed Size:  18.69 MiB
Net Upgrade Size:       0.00 MiB

:: Proceed with installation? [Y/n] n
 ezpad  ~  sudo pacman -U qt5-virtualkeyboard
loading packages...
error: 'qt5-virtualkeyboard': could not find or read package

Am I wrong in thinking "pacman -U" should see a package after running "pacman -S"?
I also looked into the PKGBUILD or the package, and if I read it properly, there should be a file in /usr/share/applications/virtualkeyboard.desktop?

ezpad  ~  ls /usr/share/applications/ | grep virt
 ezpad  ~ 
 

Also, this is about the only reference to the virtual keyboard I could find on the KaOS forums:
https://forum.kaosx.us/d/1606-on-screen-keyboard-for-tablets
I'm hoping things have advanced a bit in the past few years?

As the pacman output showed you, qt5-virtualkeyboard is part of the KaOS default install.
To learn to use pacman see https://kaosx.us/docs/pacman/

The desktop file is commented out in the PKGBUILD, since the example is no longer usable.
So, better state what your issue is and/or what you are missing/trying to do.

Sometimes we learn by making mistakes...
Do I understand corretly now that pacman -U is basially for bypassing the repos?

I'm basically trying to invoke the keyboard. Per the user guide, "Once properly installed, the virtual keyboard can be opened by clicking on a text input field." But that doesn't seem to be working in Falkon or Konsole.

Once i get into the deployment instructions, it's a combination of "presumably should've been handled by pacman", "shouldn't apply here", and "don't see where this ties into anything I understand". My best guess is i need to edit the "main() function" per loading the plugin, but i can't find any configuration files relevant to virtual keyboard and the function is not mentioned elsewhere on the page.

To make sure, did you set virtual keyboard to enabled? Systemtray > arrow icon > enable virtualkeyboard

Now I feel like i'm entering the realm of absurdist performance art...

A web search (site:kaosx.us "system tray") tells me that the system tray displays alerts when the microphone is recording, and that the icons occasionally get upgraded, so i'm assuming it's the task bar thingy. The arrow i see on that is "show hidden icons", and there is a keyboard status indicator there, but no option to enable virtual keyboard. If I right-click on the tray I get a menu with "panel options", among other things, but nothing that leads me to "enable virtualkeyboard"

A scan of the application menu shows system applications, which doesn't seem to be the right spot, and system settings which seems more on the right track, but I still can't find the relevant tabs under "Desktop behavior", "Accessibility", or "Input Devices" (which I note does not include the touch screen). Searching for "system tray" "keyboard" "virtual keyboard", and "qt5-virtualkeyboard" in both settings and applications turns up nothing, and none of those are recognized commands in CLI. I have even re-launched Croeso to see if maybe one of my icons would look like an arrow with a different theme.

I'm willing to believe that there's intended to be a simple toggle in a menu somewhere to activate the virtual keyboard, but for the life of me I can't find it. Would you believe i'm an RHCE?

You had the right place, it should look like this:
systray

Yeah, I recognize that menu, but don't recall seeing any "virtual keyboard" option.

Checked KWin options, it is only implemented in Wayland, seems they will not integrate it in X (the screenshot above is from an intel system that always runs Wayland)
What graphics drivers does your device use? inxi -G
If not Nouveau/Nvidia, try booting into a Wayland session, that will give the virtual keyboard option. Login screen (sddm) > Session > drop down menu > Plasma Wayland.

To use the virtual keyboard in an X session, run any Qt app from the terminal like this:

QT_IM_MODULE=qtvirtualkeyboard falkon

or:

QT_IM_MODULE=qtvirtualkeyboard systemsettings5

Sorry, you have to wait till I get home for any actual information:

 ezpad  ~  inxi -G
Graphics:  Device-1: Intel Celeron N3350/Pentium N4200/Atom E3900 Series Integrated Graphics driver: i915 v: kernel 
           Display: x11 server: X.Org 1.20.5 driver: intel unloaded: modesetting,vesa tty: N/A 
           OpenGL: renderer: Mesa DRI Intel HD Graphics 505 (Broxton) v: 4.5 Mesa 19.0.8

I did boot into Wayland, but the cursor response was so jumpy & laggy that it was pretty much hopeless. I did verify that the virtualkeyboard option was where you said it was, but between my touchscreen currently relying on xinput calibration to function and the aforementioned lag, I don't think it's likely to be a viable option. i did run a "top", and wayland pretty much pegged one of my CPUs @ 100%. It was something... kwin-wayland --xwayland... I think?

Back in X I did successfully launch a Konsole window with the virtual keyboard (which made me realize I'd like to figure out how to make "tab" & "ctrl-" inputs while using it).

So when you say they won't integrate "it", do you mean the menu button, or automating virtualkeyboard for all applications?
Does that mean I'd have to make that main() function edit for every application i'd like to run with a virtual keyboard?
Is there a way to restrict virtualkeyboard to only launch on a touchscreen click instead of a mouse click?

Also, completely unrelated to the keyboard, I noticed that when i rotate the screen in-app fonts seem to go haywire. Is that a familiar problem?

For Wayland, make sure to use the default windowdecoration - breeze (and most of the theme, really), 100 % cpu sounds like an aurorae based windeco.

default themes seems to have fixed the CPU issue, but the system tray seems to be a little flaky in Wayland (can't close windows once opened, not actually displaying the pop-up for "display hidden icons"), and more importantly, my touchscreen was calibrated (and rotated) via xinput; documentation for wayland calibration seems to be pretty sparse.