I have been doing more digitisation of Super-8mm and Standard-8mm movies dating back to 1962. I ran across "Unsharp Mask" in the GIMP manual and I find that Ulead Video Editing software also has this in its video filters. Looking good - on careful inspection results do not have any better detail but they seem to look better. I have found that other sharpeners do bad things with film grain but Unsharp Mask seems to handle graininess well. With "The GIMP", I am using the default settings. With "Ulead" IMO the default settings go too far and I am using relatively gentle settings of "15%, 15%" on the 2 controls provided.
Ref - info with image examples in "The GIMP" online manual:
"The Unsharp Mask filter (what an odd name!) sharpens edges of the elements without increasing noise or blemish. It is the king of the sharpen filters..."