RecyclerView with different ViewHolder using generic
From a quick glance, I share your concerns.

One 'smell' is that a sub-class (FeedWithoutImageHolder) provides less functionality than the parent class, i.e. it does not actually "extend" the class.

I suggest trying to align layout structure and functionality:

Create two different layouts: The first one without an image, and a second one which includes the first and extends it by adding an image. Depending on your desired layout design, you may instead want to declare only one layout which includes some empty placeholder element of the desired image display size which either stays empty or receives an image, so that all visual elements align.

I recommend against having a Feed handle the type of layout at all. Keep data objects and layout concerns separate, that's what the Adapter is for. Have the adapter check if an image needs to be displayed for an item and determine the appropriate view type in Adapter.getItemViewType().