I wasn't able to untlock the "Boohoo..."-achievement and therefore searched for posts about this topic. After finding a post about "you don't have every DLC installed" I manually searched for additional DLCs and then found out, that the "Dreadout DLC" is not listed/automatically installed even after selecting "every DLC" (excluding pro later) on the shop page. I had to manually click on the DLC-Page and download it.