bug#51826: qt packages (e.g. pcmanfm-qt) missing wayland qt module

[Genevieve]

> `guix shell --pure --preserve="^(XDG_|WAYLAND_DISPLAY)"
> bash pcmanfm-qt qtwayland -- bash -c
> "QT_QPA_PLATFORM=wayland pcmanfm-qt"`
> does work as expected 

Unfortunately I'm still experiencing this regression no matter
what I try, and the above command gives

    qt.qpa.plugin: Could not find the Qt platform plugin "wayland" in ""

Additionally, searching for qtwayland files in my guix profile only finds
license files in ~/.guix-profile/share/doc/qtwayland-6.3.1/...

So something is clearly not being installed, but I'm not sure where
to start with debugging this.