Dreams involving doppelgangers can be quite unsettling, as they often symbolize internal conflicts or reflections of the self. In your case, the doppelganger of your partner may represent feelings of fear or uncertainty about your relationship or aspects of your partner that you find difficult to understand or accept. The anger and disgust displayed by the doppelganger could indicate underlying anxieties about how well you truly know your partner or concerns about changes in your relationship.

The fact that this dream was particularly vivid and clear, especially given your experience with aphantasia, suggests that it may hold significant emotional weight for you. It could be a manifestation of your subconscious processing any recent feelings, fears, or situations involving your partner or your relationship dynamics.

Additionally, the setting of the dream—a farmhouse with a barn and shed—may symbolize a desire for stability and security, while the night time adds an element of the unknown, possibly reflecting fears about your future together.

To gain deeper insights, consider reflecting on your current feelings towards your partner and your relationship. Are there any unresolved issues or emotions that need addressing? Open communication with your partner may also help alleviate any anxieties that surfaced during this dream.

Ultimately, this dream may be your mind's way of urging you to explore these feelings more deeply and to ensure that you and your partner are on the same page.