Well, I've tested qt5 wayland on recent kde plasma (mint 22, mankaro etc), and it works ok (not excellent but works).
At least with Fedora KDE Plasma Desktop 41 (latest default install), Qt5 compile will not be able to position Windows. Both Lazarus and your own application have problems positioning the windows correctly.
Even Fedora Workstation 41 (latest default install) with GNOME uses wayland (so also no correct window positions with Qt5).