Metal Gear Online comes to PC through fanmade MGO2PC
Now, a new fan project is bringing Metal Gear Online 2 to PC. Through a custom build of popular PS3 emulator RPCS3, fans can connect to fan-hosted servers and play the game with all original content included from the original release. According to a comment from their official YouTube account, this custom build also makes it easier to play the single player portion of MGS4 on RPCS3, though it's not perfect yet. "Single player does work but on your first play through you'll need to do a lot of compiling shaders. After you've done a full playthrough your next playthrough will go much smoother. But yes single player does work."
You can head over to the official MGO2PC website for installation guides, an FAQ and a link to their official Discord server.