I first saw this on Gentoo Linux and have repeated on a Fedora 38 Live ISO, Fedora-Workstation-Live-x86_64-38-1.6.iso, using ReText as an example PyQt6 application:
$ sudo dnf install retext qadwaitadecorations-qt6
$ QT_WAYLAND_DECORATION=adwaita retext
QGuiApplication::setDesktopFileName: the specified desktop file name ends with .desktop. For compatibility reasons, the .desktop suffix will be removed. Please specify a desktop file name without .desktop suffix
Using configuration file: /home/liveuser/.config/ReText project/ReText.conf
Could not create decoration from factory! Running with no decorations.
Decorations do work with QtWayland's own bradient:
$ QT_WAYLAND_DECORATION=bradient retext
QGuiApplication::setDesktopFileName: the specified desktop file name ends with .desktop. For compatibility reasons, the .desktop suffix will be removed. Please specify a desktop file name without .desktop suffix
Using configuration file: /home/liveuser/.config/ReText project/ReText.conf
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Package Architecture Version Repository Size
============================================================================================================================================================
Installing:
qadwaitadecorations-qt6 x86_64 0.1.1-1.fc38 updates 62 k
retext noarch 8.0.0-1.fc38 fedora 255 k
Upgrading:
libstdc++ x86_64 13.2.1-1.fc38 updates 863 k
qgnomeplatform-qt6 x86_64 0.9.1-8.fc38 updates 164 k
qt6-qtbase x86_64 6.5.2-5.fc38 updates 3.8 M
qt6-qtbase-common noarch 6.5.2-5.fc38 updates 10 k
qt6-qtbase-gui x86_64 6.5.2-5.fc38 updates 7.3 M
qt6-qtdeclarative x86_64 6.5.2-1.fc38 updates 9.2 M
qt6-qtsvg x86_64 6.5.2-1.fc38 updates 204 k
qt6-qtwayland x86_64 6.5.2-1.fc38 updates 1.1 M
Installing dependencies:
python-pyqt6-rpm-macros noarch 6.5.2-1.fc38 updates 8.4 k
python3-docutils noarch 0.19-2.fc38 fedora 1.1 M
python3-markdown noarch 3.4.1-2.fc38 fedora 199 k
python3-markdown-math noarch 0.8-8.fc38 fedora 18 k
python3-markups noarch 3.1.3-6.fc38 fedora 37 k
python3-pygments noarch 2.14.0-1.fc38 fedora 2.5 M
python3-pyqt6-base x86_64 6.5.2-1.fc38 updates 3.2 M
python3-pyqt6-sip x86_64 13.4.0-2.fc38 fedora 76 k
xcb-util-cursor x86_64 0.1.4-2.fc38 fedora 19 k
I first saw this on Gentoo Linux and have repeated on a Fedora 38 Live ISO, Fedora-Workstation-Live-x86_64-38-1.6.iso, using ReText as an example PyQt6 application:
Decorations do work with QtWayland's own bradient: