When I moved from Qt5 to Qt6 I found an issue with the Layout in QML.

One of the items in the RowLayout needs to fill the available space, so it has Layout.fillWidth: true
But, instead of respecting the other items, it resized on top of the others. Strangely, when I manually resize the window (draging one of the borders) the layout is adjusted and it shows as it should be.

It seems that the triggering of Layout adjustment is missing in Qt6.

Snipet of the code:

RowLayout {
                    Button {
                        id: id_buttonBrowseFrom
                        Layout.preferredWidth: id_labelRef.width*8
                       ...
                    }
                    Button {
                        id: id_buttonSshFrom
                        Layout.preferredWidth: id_labelRef.width*8
                       ...
                    }
                    Rectangle {
                        id: id_rectFrom
                        Layout.preferredWidth: id_labelRef.width*10
                       ...
                    }
                    TextField {
                        id: id_fieldFrom
                        Layout.fillWidth: true
                        ...
                    }
                }

Screenshot of how it looks when the application starts:

Screenshot of how it looks when I resize the window and adjusts automatically: