I don’t know what’s actually going on, but I can’t see the rendered preview in 2.91 when I have Cycles selected. It still shows that I moved the viewport along, but it doesn’t actually update the viewport when I do.
Like I said, I don’t know what’s going on, if I need to update my drivers, if it’s just an issue with AMD cards and Blender not playing well together, or if it’s just a bug in 2.91, but it either takes too long to load or doesn’t load at all when it comes to “Rendered” mode in the viewport.