I'll have to look into that. It should just work since it works on Chrome and I've made effort to request as little privilege as possible. But I'll have to test and try it out.
So yeah checking. Apple stopped making Safari for Windows a long time ago. So the issue with me supporting it is I have no way to test before publishing. I'll need to figure out something for that if I want to make the Safari version a real boy.
If you're able and willing, create an issue on the addon repo: https://github.com/chris-mosley/AmazonBrandFilter/issues
And I'll build a version for safari for you to test.