Two different segments want very different things.  

It has bugs and is still in alpha.  

New news today I updated my version of Artcraft for Linux.   I discovered that they updated it; there are even new programs for making 3D and 2D art.   A Figma clone. Build tileable PBR materials from noises, patterns and filters in a node graph, watch them update live in 2D and on a 3D model, and export the maps for any engine. Open source, offline, and yours.   Paint PBR materials straight onto your models in layers with masks, bake mesh maps, drive smart materials from them and export textures for any engine. Open source, offline, and yours. This other one is a clone of Substance Painter.  

Yes, and I add more animals create by @Duileoga.

Here is an intermediate release of mercator, now being updated to version 0.14.0. There are a lot of changes "in the engine room" increasing processing speed and (hopefully) making map editing and manipulation a bit easier. There are also a large number of bugfixes (please have a look at the changelog). The tool and its documentation and changelog is available at the initial post of this thread in https://wildfiregames.com/forum/topic/169940-new-atlas-helper-tool-mercator/