I’ve tried it on both “Arch” “GNU/Linux” and the “Fedora KDE Plasma”. I’ve had the same issue. Yes, I understand that I’ve applied cosmetic customization, but turning them off by resetting to the default theme doesn’t seem to fix them. Nor does updating and rebooting my operating systems. Nor does deleting thumbnails using rm -rf ~/.cache/thumbnails/. Nor does installing packages with sudo dnf install kio-extras ffmpegthumbs kdegraphics-thumbnailers. I hesitated to file a bug though, because I don’t understand how I can have the same problem across multiple machines and be unable to fix it, yet can’t seem to find anyone else with a screenshot of the exact same problem.
One clue is that it seems to be a problem with the grid view (visible by default upon opening Dolphin) but not the list view (visible by default upon uploading or selecting an image using one’s web browser).
It was resolved by resetting all settings and rebooting. I am sure it was Dolphin and just resetting the theme alone wasn’t enough because I’d tried that before.
The problem wasn’t or wasn’t only a third party theme. After double-checking and reproducing the problem I determined that the problem is due to the font management somehow. My theme is set to breeze and I’ve rebooted. I don’t know why the transparency that typically comes with breeze isn’t apparently present.
Upon adjusting all fonts to Terminus and then closing and re-opening Dolphin, the issue occurs again. Regardless, I think that changing fonts and themes within reason without breaking Dolphin should be supported.
I’ve reproduced it again on Fedora. It’s setting the general font specifically
System Settings → Appearance & Style → Text & Fonts → Fonts → General → Select Font → Font → Terminus → OK → Apply
The problem is inconsistent in at least one respect: Places → Trash and Recent → Recent Files and Recent → Recent Locations don’t show the issue. All other “Places” and “Devices” do, at least on my machine.
Ah, I see: xos4 works but plain Terminus does not, yet still shows in the menu and appears to work on existing windows, at least until new windows are opened. I guess that solves this for me. I still don’t understand what the difference between xos4 and just “Terminus” is.
