The “save as” dialogue is missing the file type selection option. I writer there is no way to save a document as a .doc or in any format other than .odt. Similarly in calc etc.
My OS is Ubuntu 16.04. The problem occurs both with the default version (5.1.6) and with the “fresh” version (5.3.3, installed using PPA).
I remember dealing with the same problem years ago, also on Linux. Probably it was still named OpenOffice then. Somehow it got solved but I don’t remember how. Please help.