Just a comment, results are ok but not identical between versions.
This using kubuntu 20.04 / Gimp 2.10.36 / same image / same stack of tiles.
New version has lost some of the definition. The background has the same pattern as the adjacent foreground.
Looking at the resulting layers. The mask is inverted ? Well maybe not inverted but not the same ?
This using kubuntu 20.04 / Gimp 2.10.36 / same image / same stack of tiles.
New version has lost some of the definition. The background has the same pattern as the adjacent foreground.
Looking at the resulting layers. The mask is inverted ? Well maybe not inverted but not the same ?