Edit the "pluginrc" file in your
Gimp profile, the section for the plugin that loads jpegs it should look like this:
(plug-in-def "/usr/lib/gimp/2.0/plug-ins/file-jpeg" 1494589442
(proc-def "file-jpeg-load" 1
"loads files in the JPEG file format"
"loads files in the JPEG file format"
"Spencer Kimball, Peter Mattis & others"
"Spencer Kimball & Peter Mattis"
"1995-2007"
"JPEG image"
0
(icon stock-id -1 "")
(load-proc
(extension "jpg,jpeg,jpe")
(magic "6,string,JFIF,6,string,Exif")
(mime-type "image/jpeg")
(thumb-loader "file-jpeg-load-thumb"))
""
3 1
(proc-arg 0 "run-mode" "The run mode { RUN-INTERACTIVE (0), RUN-NONINTERACTIVE (1) }")
(proc-arg 4 "filename" "The name of the file to load")
(proc-arg 4 "raw-filename" "The name of the file to load")
(proc-arg 13 "image" "Output image"))
(proc-def "file-jpeg-load-thumb" 1
"Loads a thumbnail from a JPEG image"
"Loads a thumbnail from a JPEG image (only if it exists)"
"Mukund Sivaraman <muks@mukund.org>, Sven Neumann <sven@gimp.org>"
"Mukund Sivaraman <muks@mukund.org>, Sven Neumann <sven@gimp.org>"
"November 15, 2004"
""
0
(icon stock-id -1 "")
""
2 3
(proc-arg 4 "filename" "The name of the file to load")
(proc-arg 0 "thumb-size" "Preferred thumbnail size")
(proc-arg 13 "image" "Thumbnail image")
(proc-arg 0 "image-width" "Width of full-sized image")
(proc-arg 0 "image-height" "Height of full-sized image"))
Note the "load-proc/extension" item. What extensions are listed in yours?