It will very much depend on your degraded image, there might be more than just jpeg artifacts to play with.
Not much available on creating artifacts other than exporting an image a couple of times with low jpeg quality settings.
There is a filter in the gmic plugin http://www.gmic.eu The latest version is a bit picky about installation
see: https://www.gimp-forum.net/Thread-Instal...ws-10-demo
edit: I see you are using linux. Dead easy, get one of the zips, unpack, pop the gmic_gimp_qt file in your Gimp profile ~/.gimp-2.8/plug-ins
At least it gives a preview for the result. This before/after
![[Image: 1752pPH.jpg]](https://i.imgur.com/1752pPH.jpg)
Not much available on creating artifacts other than exporting an image a couple of times with low jpeg quality settings.
There is a filter in the gmic plugin http://www.gmic.eu The latest version is a bit picky about installation
see: https://www.gimp-forum.net/Thread-Instal...ws-10-demo
edit: I see you are using linux. Dead easy, get one of the zips, unpack, pop the gmic_gimp_qt file in your Gimp profile ~/.gimp-2.8/plug-ins
At least it gives a preview for the result. This before/after