There is a serious bug in the Linux version V1.52 at Gog.com. After installing the version incl. DLC you start in the cellar not with Benedikt as a child, but with Viktoria. The cellar door cannot be closed and there are no objects to interact with.
According to Red Martyr, this problem was fixed with the latest bug fix in v 1.53. The patch was released over a month ago.
Could gog.com please upload Saint Kotar version 1.53 on the GOG website.