Everyone's favourite Linux games launcher has added yet another milestone feature thanks to Linguin and other Heroic contributors. The development version of Heroic now uses a project named comet to translate a game's GOG Galaxy API calls using a platform-agnostic SDK.
There are prebuilt solutions in some common engines, and companies like Multiplay that will help with development and hosting, but ultimately it depends on the specific needs of each game.
What works well for one project might be overkill for another, so studios have to spend a lot of time figuring out their needs and building something bespoke for it.