I’m wondering if this is reproducible and whether it is an openSUSE issue or KDE issue.
Populate a folder with many medium to high resolution photos. I used this the photos fromthis archive:
Configure KDialog for “Short View” with “Show Preview” toggled on
Using web browser that uses KDialog as file picker, navigate to site that gives option of upload in an image e.g. imgur.com
Select the upload link on site to open KDialog
Navigate to folder containing images from step 1
Immediately begin scrolling before all thumbnails have rendered
Many thumbnails will not render unless they are hovered over
This issue is not present for me if I pause a few seconds before I begin scrolling once I navigate to an image-filled folder.