
The extension can be found in the Extensions menu > Export > JPEG Export. Just drop the two jpegexport.* files in your extensions folder (usually ~/.config/inkscape/extensions on Linux or %APPDATA%\inkscape\extensions on Windows). This method doesn't have any problems with clips, masks and images but is much, much slower than the one above if you have many objects selected.
normal mode export calls a command line Inkscape instance for every selected object to get its data. In any other case this is the recommended method since it is much, much faster than the one below This has some issues with masks and clips, and, in Inkscape versions prior to 0.49, with images. fast mode export uses Inkscape's simpletransfor library to determine area and position of the selected objects and exports them. full page export exports the whole page. This extension simply exports a PNG image and then converts it to JPEG using ImageMagick this means that you must have ImageMagick installed to make it work. It is one of my first works in Python and is developed for my personal needs, so I will be glad if you find it useful, but I can't say if it will work for you too. This is a small and basic Inkscape extension that allows to export directly to a JPG file instead of the standard PNG. Work is needed to port it to Inskcape 1.x.
NOTE: This plugin only works with versions of inkscape prior to 1.0.