G’Mic or GREYC’s Magic for Image Computing is an opensource filter framework, or, it is an extra program you can download to have access to a whole lot of image filters.
Krita has had G’Mic integration for a long time, but this is its most stable incarnation.
You set it up as following:
First download the proper krita plugin from the G’Mic website.
Then, unzip and place it somewhere you can find it.
Go toand set G’MIC to the filepath there.
Then restart Krita.