@Pavel yannara Mirochnitchenko, Thanks for posting in Q&A. Based on my test, the GIMP is not supported in preview.
I think this can be in preview stage. So some apps are not available yet. You can contact the app support to see if they have successfully uploaded the app into Microsoft store new. If the app has already uploaded, you can contact Microsoft store support to look into the app in the background to help on this.
Hope the above information can help.
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