I've never used this type of import. I'm using XnView MP for macOS, where I select several image files and drag them onto a page in Scribus.
Your sample showed a *.png, which can have some weird subformats (interlaced, reduced colors, transparency, even all 3 versions in one file). Did you ever try to place a JPEG or TIFF file? Just tried these formats with your method here (huge 48 bit TIFF with 635 MB), everything is perfect, though it takes some time to be displayed in the preview area.
BTW, because the browse window is kind of small, it might help to scroll sideways or to enlarge it to see more folders on your machine.