Running Microsoft office on WINE (WINE Is Not An Emulator) on a *nix, typically on a self-hosted “cloud” you set up in your basement. CrossOver uses WINE, so it would also count. Office WINE typically arrives in rectangular shaped package boxes delivered from a nearby CDN by your friendly neighborhood package manager.
Dude, I love WINE so much! Pouring it in an easy no-spill cup of Linux Mint makes for some pretty good Office WINE.