Bungie has stated that they plan to achieve cross-platform cross-play by 2021. This date could change, but it’s something they are working on implementing soon. If you currently play on Xbox, Playstation, PC, or Stadia, then you will be able to cross-play with people that use the same console, even if they have an older version, but you won’t be able to use your PS4 to play with someone on an Xbox, for example, until at least 2021. There is also no support for macOS, and there probably won’t be any time in the future. Mac users can either dual boot through Bootcamp, or use a service like Nvidia’s Geforce Now, which allows users to stream games to any computer, regardless of the operating system.