For me it's three games(out of 24) in total. Most recent example is Rage 2(added yesterday). The second one is Void Bastards. As for the third... I don't remember what it was.

So... what's up with that? Does anyone know?

Hah I just installed Rage 2 and was googling if someone has the same issue :)

I was hoping this was already resolved and Galaxy would be able to recognize everything added to Game Pass no matter how recent, but guess not.
So for now I will have to launch Rage 2 from its icon outside Galaxy I guess.

Rage 2 is broken for you too? Does it mean that this problem pertains to specific games?

Can you check whether Void Bastards will behave the same for you?
(Unless you don't feel like messing up your game collection. That's cool.)

Hopefully someone from the GOG Team will see this thread.)

Yep, Rage 2 also shows up as unknown game. So I hid its icon for now.
I do not have a free space at the moment to be downloading anymore games, already have Fallen Order and few others to finish, but I suspect Void Bastards would be missing the info as well.

Here is hoping GOG team does monitor these forums.

Rage 2 showed up in my library.

I added the data manually but yep, now it shows correctly.

right click on the game and edit?

Oh, wow. I had no idea these edits go out to everyone!

Also, an easy way to identify an unknown game is to go to its "My progress" section. If the game has achievements, GOG2.0 will straight up list all of them for you. ...somehow.