I would like to edit a JPG EXIF data in Gimp. Perhaps I need a plugin or something, but I don't know how to search for and download the plugin. Plus, when Gimp opens a JPG it converts it to XCF format. Hopefully when I export it again the EXIF data will still be there. Thanks.
As of Gimp 2.9.4 (possibly 2.9.2) there is a built-in metadata editor/viewer. It is under the menu > Image > Image Metadata.
If you are on OSX and want a binary of this version (rather than compile from source), try Partha's McGimp variants, the McGimp 2.9.5 64-bit Experimental, or McGimp 2.9.5 64-bit Color Corrected Experimental, an interesting project in its own right.