Whilst none of the core Syncplay developers have Mac OS X, we are aware that some of our users do have it.
solarnz has helpfully written a guide to installing and running Syncplay on OS X with the aid of Homebrew.
With his permission we have now adapted the guide for the Syncplay website. See: https://syncplay.pl/guide/osx/ for the guide.
Let us know how well it works, which players it works with, and if there are any changes needed to the guide.
(p.s. RC3 has problems with MPV 0.3 – this is fixed in the development version, and will be fixed in RC4)