If you want something similar, but better and cross-platform and 5x more expensive, definitelly try Axure RP.
PS: I feel your pain. When I went Mac-first a while ago, there was this little graphics software called Xara that just worked in a way that I can only compare with Sketch. There was nothing close to it on the Mac. I missed it for a while, I begged the creators to port it, then just moved on.