I haven’t used either, but a quick search recommends two that, used in combination, can handle some of what GIMP can do.

https://www.teddit.net/r/GIMP/comments/r4ld07/is_there_a_gimp_for_android/

There’s nothing that is exactly like GIMP. I had an app called XGIMP, but it is practically useless IMO. If you want something similar to GIMP on mobile, ibisPaint X is free and has similar layer capabilities (Layers, Layer Groups, and Layer Modes); it also allows you to import multiple images into separate layers and modify them. I use this if I want to sketch on my phone. If you want capabilities like the Colors/Tools/Filters dropdown menus, Fantasia Painter is also free and would probably be what you want, though keep in mind everything is done on a single layer. I use that if I want to do mobile photo manipulation.

https://play.google.com/store/apps/details?id=jp.ne.ibis.ibispaintx.app

https://play.google.com/store/apps/details?id=com.datcompany.fantasiapainter