You need to find Goatskin as a part of the main quest “Into the Underworld” in Kingdom Come: Deliverance 2. Katherine informs you that he might have more information on the whereabouts of John of Liechtenstein, as he is rumored to be spying for a noble. You have very little information about Goatskin’s whereabouts and a lot of ground to cover, so getting him can be tricky. This article will take you through the exact steps to find Goatskin.
Goatskin In Kingdom Come: Deliverance 2
Method 1

You need to talk to Udo Von Tauberbishofshiem and bait him to find Goatskin. Head over to the City Bathhouse in the southwest portion of Kuttenberg to find him sitting at a table by the window. If it isn’t already, skip the time to late night hours, ideally between 22:00 – 3:00. Introduce yourself and start a conversation with him.

Your main motive here is to send him home by any means, and you have two options: either choose “I think you should go home” and use skill checks on him, or beat him at dice three times. Whatever means you use, start following him once he gets up to leave.

It takes quite a while, but on his way home, Udo Von will come across two wagons. This is where he gets ambushed by Goatskin. He tries to mug him, so you can let him continue or interrupt. If you interrupt, Henry will tell the German Man to go home, and you can ask Goatskin whatever you need to know.
Method 2

There is another method to talk to Goatskin, where you need to find out his hideout. There are no hints given as to where it might be, so you have to rely on checking each and every house, barn, and shed in the highlighted area. This one has to be specifically done during the day, ideally between 8:00-17:00. This method was reported as bugged for now, and I myself needed two reloads before I got the talk prompt.

Go to the location shown above, enter the barn in front of you, and climb up the ladder. Navigate through the top floor, and jump down from the door at the other end. This place is not accessible otherwise, as it is surrounded by high, non-climbable walls and locked doors all around.

Use the cart with wooden planks on it to climb in through the window above it, where Goatskin is sitting on the left. Upon interrogation, he starts blabbering about a guy named Samuel. Tell him you know a place where he can hide for the best results and a positive reputation. He then reveals that he has been spying for the last few weeks for a guy named Samuel, who might know more about Liechtenstein. You can now proceed towards your next objective in the northeast side of Kuttenberg.