There's some nice GIMP tutorials here with good showcasing. https://pixls.us/articles https://pixls.us/articles I believe written by GIMP contributors.. includ

There's some nice GIMP tutorials here with good showcasing. https://pixls.us/articles https://pixls.us/articles I believe written by GIMP contributors.. including Pat David who did a ton of older and a bit less polished ones here: https://patdavid.net/getting-around-in-gimp/ https://patdavid.net/getting-around-in-gimp/ (for example this good one from 2012 https://patdavid.net/2012/08/getting-around-in-gimp-heal-selection/ https://patdavid.net/2012/08/getting-around-in-gimp-heal-sel... )