I usually just start an onscreen keyboard but I look forward to smarter folks telling me the way...
KDE
KDE is an international technology team creating user-friendly free and open source software for desktop and portable computing. KDE’s software runs on GNU/Linux, BSD and other operating systems, including Windows.
Plasma 6 Bugs
If you encounter a bug, proceed to https://bugs.kde.org/, check whether it has been reported.
If it hasn't, report it yourself.
PLEASE THINK CAREFULLY BEFORE POSTING HERE.
Developers do not look for reports on social media, so they will not see it and all it does is clutter up the feed.
I think Wayland Qt apps start the keyboard automatically when I focus a text box. It works in Firefox, for example. Doesn't seem to be the case for Xwayland apps and I haven't tested Gtk.
On my Thinkpad 2in1, the behavior your desire is what I get. I'm on Fedora KDE (Kinoite) which pre-installs Maliit by default though, I'm not sure if it comes with some additional configuration.
The help page of virtual keyboards mentions detecting a hardware keyboard, but that's all I know. Does it not detect the keyboard built into my laptop? It makes no sense to me lol.
How do you start that? Is it a seperate package? I never even saw it but really curious