What you are seeing in the photo is a specific type of lens flare known as ghosting. It is an inverted and reversed reflection of the brightest highlights of the scene. If you were to draw an x and y axis intersecting in the center of the photo, all of the artifacts in the photo have corresponding bright light sources at the same distance from center and at the same angle from vertical and horizontal on the opposite quadrant.

Digital sensors are much more reflective than film was, and additional care must be taken to reduce the effects of ghosting when designing lenses to be used for digital cameras. But even the best designs have their limits. Any scene with bright light sources will demonstrate some ghosting, but it is usually not noticeable if the rest of the scene is bright enough to hide it. When there is such a large difference between the brightest and darkest parts of a scene, though, then reflections that fall in areas that are dimmer will be much more noticeable. For more, please see Does high reflectiveness of digital sensor lead to poor lens performance?

The artifacts are visible in an EVF because the main sensor is being used to create the image seen in the EVF. This allows light to bounce off the front of the sensor stack, onto rear surfaces of lens elements, and back to the sensor. If one were to use a traditional DSLR, the artifacts would not be visible in the optical viewfinder when the mirror is down and blocking the light from the lens reaching the sensor (even if the shutter curtains were open).

For suggestions on how to deal with ghosting, please see this answer.

Here's an obvious example of ghosting that is easy to see due to the very bright lights and the very dark areas in the same scene.

Here's an external view of the house pictured in the question. One can see the railing on the second floor balcony that is reflected, upside down, in the images taken from inside the upstairs front bedroom.