GIMP - New in the development branch: the Smudge tool can now sample colors from all visible layers, so you can smudge on a separate layer and keep the original data untouched.
GIMP 2.10 Tool Preset Fixes by PkGam on DeviantArt
GIMP Smudge tool not working?
Smudge tool changed! (2020) — Help & Support — gimpusers.com