There are some games, which are buyable on Steam (in my case Assasin's Creed Revelations), but require a uplay account. How can you find out which uplay account is linked inside Steam?
It seems that the CD key is already taken and so I guess it's another uplay on which I activated the game (I used to play it) despite not remembering of having ever created another uplay account.
So is there any opportunity to do so or will it probably an issue for the ubisoft service?
No there is no way to find out which Uplay account is linked to which game.
If you have multiple accounts of Uplay then you have to be careful about which account is signed in. Steam clearly gives you keys which you have to activate on Uplay client.
As for your case, you must remember the email ID of the Uplay account otherwise, I am afraid even Uplay Customer support won't be able to help you.
I also had the same problem with Far Cry 4 and I accidentally fixed it by first logging out of my current Uplay account(the wrong one) and trying to relaunch the game from Steam. Somehow Steam just logged me into the right Uplay account with my Far Cry 4. I guess Steam also remembers which Uplay account was linked to your game.
I recently had the same problem and I contacted their phone for United States (you can find their phone by searching it up on google) and I sent in a ticket and told them what happened.
They said that if I give him the CD Key they could track it down and then they asked me some questions regarding the email and then they told me the email name.
