What's the problem with making a circle with the select tool and then tracing it or filling it? It's not hard to make a circle in GIMP...
That's not a circle, that's a grid of pixels being colored in. It's a lossy representation of something else.
A circle is a shape which is a graphics primitive. Graphics primitives can be moved, transformed, skewed, etc... with no loss of information.
If you do that with a grid of pixels, you're going to lose information.
Edit: Five downvotes. Apparently people don't know how to use vectors in bitmap authoring software, or why selections are the lossy way to create shapes. See details in my comments below.
You want a vector editing software like inkscape. GIMP only does rasterized graphics.
Raster editing programs can support vector shapes. They are rasterised during export, not when the shape is created.
Look at how to create, move and transform a circle in photoshop (or if you don't want to give adobe money, use photopea).
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Hopefully this upgrade involves a shape tool to draw a circle.
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