Available and installed games from service like Xbox Game Pass for PC may be accessible through GOG Galaxy 2.0?

They dont show up for me. At least not the available games, i have jet to install one. It only shows xbox one games and even there only a hand full of the ones i own. It only shows 4 of my games that i have installed on xbox one, not showing any of the available ones there either.

The xbox integration only sees games from my Xbox (Beta) app if I have them installed and have booted them up at least once.

It's not fully functional as of yet because you can't manage your installs, or even launch them currently.

In my case it only shows the games I have on Xbox (console) and that doesn't even work well because it lists all games I have installed from Game Pass (again, on the console, not on my PC, which I also use) and there is no way to tell if a game is owned or rented.
Also, it does not show Xbox 360 retro-compatible games, but that's understandable. I hope that's added later.

In my opinion subscription services should have a dedicated integration to avoid confusion or, alternatively they should have a special label and they should be removed when you are not subscribed anymore or they rotate out of the servic. In my case for example I still have Hitman 1 in the library even if it was removed from Game Pass.

It's now December 2019 as I write this and I just installed the client as open beta gets going. For posterity (people reading this thread later), I got my PC Game Pass working perfectly well by having Galaxy log into my MS account and then playing one of my installed games. After restarting Galaxy, it synced every game I've ever installed or played. Very very well done.

What do you mean with ""having Galaxy log into my MS account "" ??? How do I do that?

Settings->Add Games and Friends->Connect Platforms->XBox Live

Follow the directions after that to get games from your MS account (your store and games that you've installed before under the game pass if you have a subscription). This doesn't include actual XBox games, just PC games available through the Windows Store.