In this video, I see that for hours, it seems that the flow keeps going from the 11h direction to the Sun's surface - while there looks like nothing is coming to the top of the loop to provide a source for the flow. Where does it get all that material?
Good question. The material comes from the Sun, is ejected into the loop quickly, and slowly rains back down.
In the linked video at timestamp 0:11 you see the complete Sun and the flare erupting on the right rim of it. More close-up at 0:28 you see the loop already faintly and much smaller. It is then brightening up quickly and expanding. That is material erupting from the Sun and filling the magnetic arc(s). Subsequently you see that most of the ejected material slowly rains back down, mostly along the lines of the magnetic field while some small part will continue to expand and might arrive here (if that was direction to Earth) and trigger some nice polar lights.