I stumbled upon one interesting extension for GIMP, and remembered how everyone
rushes / worn with a new chip in Photoshop - smart fill / delete.
For a start, it is worth remembering that somehow, though very bad, you can use
Content Aware Resizing algorithms for the same purposes.
And recently I found in the overlay extension
resynthesizer for GIMP. Judging by the date he is at least six months.
I took the panorama from the previously mentioned
topic and made the Heal selection. A couple of drawbacks: if you select everything you need to remove, then clouds may appear from the top of the picture, so I “deleted” from each edge separately. Well, glitches around the edges are most likely due to the fact that the picture is small and the reduced ponaram had smooth edges.

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By the way, the closest person it removes suspiciously equally with Photoshop. But the mountains in different ways. True, there you can choose the size of the texture search area, so this may be the reason.
In addition, the extension is able to wildly-do "smart" (but strange) scaling. In comparison with the bicubic interpolation method:

He knows how to make seamless textures from images, and it turns out that he has a better standard extension for GIMP. For example, from
this I could get this:

And you can also do some strange manipulations with several input images ... I myself did not dare to experiment, so you can
look at the site