I'm only aware of the 9 Holmberg "dwarfs" that Uwe has observed with a 16", at the link he posted earlier. These are also listed as an observing project in the book "Galaxies and How To Observe Them" by Wolfgang Steinicke and Rich Jakiel (I love this book!).

I liked the idea of a short, but challenging list, so several years ago, I finished all 9 with my 18", with Holmberg IX being by far the hardest for an 18" (although I've seen a great view of it through Josh Wright's 25" at TSP 2012). I posted some of my observing reports in the Austin Astronomical Society's newsletter below (scroll to page 18)
http://austinastro.wildapricot.org/r...e/st201607.pdf