09-29-2021, 08:02 AM
It all depends on the image being processed. If C2A removes a colour, paint it back in on an under-layer or use the paint tool in behind mode.
For that image, with small areas that tend to remain with some plugins, try fuzzy selecting the BG while adjusting the selection threshold. Gimp 2.10 has a threshold mask which clearly shows the selection and is adjusted by dragging the mouse across the canvas. If (when) that removes too much, then as before, repair the missing sections, (paint mode behind)
Sometime helps if a temporary layer (grey or blue) is under to help spotting the areas to repair.
example: https://i.imgur.com/2QJDmkz.mp4
For that image, with small areas that tend to remain with some plugins, try fuzzy selecting the BG while adjusting the selection threshold. Gimp 2.10 has a threshold mask which clearly shows the selection and is adjusted by dragging the mouse across the canvas. If (when) that removes too much, then as before, repair the missing sections, (paint mode behind)
Sometime helps if a temporary layer (grey or blue) is under to help spotting the areas to repair.
example: https://i.imgur.com/2QJDmkz.mp4