The latest update (build 2134911) addresses the menu screen crash for Mac players. Highscores are still not visible, but that is being worked on! More info in the previous update-- http://steamcommunity.com/games/94400/announcements/detail/3121415195625216506
Nidhogg update for September 20, 2017
Menu Screen Crash Hotfix (now for macs too) 9/20/17
View all patches · Build 2134911 · Last edited March 15, 2019 – 19:00:11 UTC by 
Wendy
Patchnotes via 
Steam Community