Bug 406180 was fixed in Plasma 5.16 and later by commit
0124b1ef191fcafe0d0f89287be66b36833586e6, which
disables vsync for QtQuick windows. However, a bug
in Qt prevents this fix from taking effect for any release
prior to this commit
https://code.qt.io/cgit/qt/qtbase.git/commit/?id=0c1831178540462da31fd7a4b6d2e446bc84498b
As a workaround for users stuck with an older Qt version,
this change detects whether PRIME synchronization is
enabled for any output, and if so, forces QtQuick to use
software rendering.
BUG: 406180