If you do not have the option to save or open a particular filetype in Inkscape, check the extension-errors.log file (~/.inkscape/extension-errors.log for Linux or %userprofile%\Application Data\Inkscape\extension-errors.log for Windows) for details about what dependency was not met for the filetype.
For example, I cannot save AI files and this is was extension-errors.log says:
Code: Select all
Extension "AI 8.0 Output" failed to load because a dependency was not met.
This means Ghostscript (gs) is required and cannot be found. This may mean Ghostscript is not installed, or it's path is not in the PATH environment variable.
Note that a required dependency may not be available for your platform (i.e. some dependencies might be available for Linux but not Windows). Also, if a filetype is not listed in Inkscapes save or open dialog and also not mentioned in extension-errors.log then it isn't supported.
*** Alternatively, and perhaps more conveniently:
Inkscape is quite good at opening PDF files, so convert your file to PDF and open that with Inkscape instead.
Acrobat Reader can open some AI files and save them as PDF. It may be able to convert other formats also. You can also use Document Converter eXpress to convert EPS to PDF.