I am on the latest trunk of Linux. But, version 1.8.2 also has the same problem. Windows is OK.
* On a new form add a TPageSetupDialog and a button.
* On the click event of the button run:
* The setup dialog will be displayed, but with empty Margin values.
* If you change the Margin values, nothing happens on the sample page in the dialog box.
* If you close and click again on the button to reopen the PageSetupDialog, the margin values are again empty.
* The Margins group box does not display any metric (like "inches")
* There is a useless "Printer..." button at the bottom right.
* "Source" is disabled.
* We have also a funny tab order for the controls on this dialog box.
And; yes, I do have a default printer defined on the system.
System:
Ubuntu Linux 17.10 / Gtk2