You might be able to make use of the script in the zipped folder below which converts single black pixels to white. It was written for use with RGB (no alpha channel) image mode so you would have to convert your mono image to RGB, run the script then convert back.
Please note for the script to work, the converted black pixels must be black 0,0,0 and the 8 pixels surrounding it must all be white 255,255,255
If you wish to try it place the script in your plug-ins folder, restart Gimp and it can be found at menu bar, '<Image>/Filters/Remove single black pixels'
It works on my Gimp 2.10.36
Hope it works for you
EDIT I've just noticed an omission from the script
Before running the script ensure the background colour is set to white 255, 255, 255. If it isn't any single black pixels on the very edge of the image will remain
Sorry for this
Attachment:
remove-single-black-pixels.zip [924 Bytes]
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