Distro pyside6 builds linked against system Qt pick up the system
platform theme plugin (Breeze on KDE, Adwaita-ish on GNOME, etc.),
which gave AUR users a different widget style than the source-from-pip
build that uses bundled Qt. Force Fusion in the no-custom.qss path so
both routes render identically.
The inherited palette is intentionally untouched: KDE writes
~/.config/Trolltech.conf which every Qt app reads, so KDE users
still get their color scheme — just under Fusion widgets instead
of Breeze.