It will depend on the source image used. Your example, obviously an illustration, whereas a photgraph is probably going to be more complicated.
However you could try (photograph)
Apply a median blur Filters -> Blur -> Median Blur
Cartoonise Filters -> Artistic -> Cartoon
Desaturate using GEGL C2G Colors -> Desaturate -> Color to Grey
example: https://i.imgur.com/eQD08xb.mp4
edit:
I was playing with this plugin before suggesting the standard Gimp filters above. Again it is a 'cartoon' effect smoothing the image colours. see: https://www.gimp-forum.net/Thread-Additi...5#pid23165 for the link (gimpscripts) to the plugin. It uses a big Gimp plugin gmic_gimp_qt from http://www.gmic.eu you need that as well.
This procedure:
Apply the plugin which installs to Filters -> Artistic -> Comic Book for 2.10
Makes a very colourful image, so desaturate Colours -> Desturate -> Destaurate
I want the black a little blacker so finally use the color-curve tool.
another example: https://i.imgur.com/W9SMs4A.mp4
However you could try (photograph)
Apply a median blur Filters -> Blur -> Median Blur
Cartoonise Filters -> Artistic -> Cartoon
Desaturate using GEGL C2G Colors -> Desaturate -> Color to Grey
example: https://i.imgur.com/eQD08xb.mp4
edit:
I was playing with this plugin before suggesting the standard Gimp filters above. Again it is a 'cartoon' effect smoothing the image colours. see: https://www.gimp-forum.net/Thread-Additi...5#pid23165 for the link (gimpscripts) to the plugin. It uses a big Gimp plugin gmic_gimp_qt from http://www.gmic.eu you need that as well.
This procedure:
Apply the plugin which installs to Filters -> Artistic -> Comic Book for 2.10
Makes a very colourful image, so desaturate Colours -> Desturate -> Destaurate
I want the black a little blacker so finally use the color-curve tool.
another example: https://i.imgur.com/W9SMs4A.mp4