They do, there will be a Linux penguin on the supported OSes list if the game has native support for Linux.
If the game doesn't have native support, and you buy the game on a Linux machine, it will warn you about possible incompatibility.
In any case the reality is that every game I've bought on GOG has worked pretty much perfectly on Wine, I use winetricks.
The main problem with Windows games these days is the DRM which on Wine will crash. Good thing GOG games don't come with any.
They do, there will be a Linux penguin on the supported OSes list if the game has native support for Linux. If the game doesn't have native support, and you buy the game on a Linux machine, it will warn you about possible incompatibility.
In any case the reality is that every game I've bought on GOG has worked pretty much perfectly on Wine, I use winetricks. The main problem with Windows games these days is the DRM which on Wine will crash. Good thing GOG games don't come with any.
It's a website; it works just fine on Linux.
If you want a fancy launcher, there's always Heroic.
Note that they recently were hiring someone to work on the Galaxy launcher for Linux