@david Sorry if maybe I’m telling you something that you already know, but I’ve been using Gimp for many years and I only recently discovered that you can rotate an image without blurring it. All you have to do is to use the Rotate Tool with “Interpolation: NoHalo”. It’s not the default setting in the Gimp, and until I discovered it, I was terrified whenever I had to use the Rotate Tool.
Forgive me if my comment is not helpful.