Our layout example can be used as reproducer:
https://doc.qt.io/QtForMCUs-2.8/quickultralite-layouts-example.html

Upon launching, the GridLayout is going to look like this:

So it looks as if GridLayout is not doing anything, and all of its components are positioned at the same coordinate.

Nevertheless, if one touches/clicks the "columns" button and toggle the GridLayout between different column limits, then it starts to look right. For example, when the column changes from -1 back to 0 again, it looks fine (just a single row with its column count maximized).