Yes. Read the previous posts and develop with Lazarus against Qt instead of GTK. Or run your code under Wine. Or create a patch and submit it to the Gtk developers so they can change Gtk combobox behaviour. Or use customdrawn components (if they are ready for this), or use MSEGUI, or use fpGUI.
IIUC, you're upset about different combobox behaviour on Gtk2 versus Windows, while the combobox itself works fine on Gtk2. Looking at the posts above, I don't think there's any chance tis will be changed.