Bug 472336

SUMMARY
This is a wild guess this belongs to xdg-desktop-portal-kde subproject. I'm not an expect. See Summary section as well. If  you think it should belong somewhere else please move it or guide me where I should report it again.

STEPS TO REPRODUCE
1. Open https://blogs.sitepointstatic.com/examples/tech/filedrag/1/index.html in Chromium based browser (Chrome) and in Firefox (for comparison)
2. Create a folder named "płacz" (there is polish letter ł here)
3. Copy any non empty file to this folder
4. From Dolphin drag the file into Chrome to the drop box on the page you opened in step 1

OBSERVED RESULT
In the "File information" section you will notice it has size of 0

EXPECTED RESULT
It should be able to read the real file size

if you repeat this experiment with path (and filename) containing only a-z characters (like /home/user/Documents/whatever.pdf) it will be read correctly by Chrome. Firefox however always reads the file correctly.
The Browse/Choose file button works with this demo page. However it causes issues with GMail interface (it rejects any attachment files, even via a button, because they are empty).

This COULD be the Chrome bug. Something similar was reported 13 years ago: https://bugs.chromium.org/p/chromium/issues/detail?id=42494 and in this thread you can find a reference to some old Dolphin bug again. 

But on the other hand I found this post, suggesting it's because of `xdg-desktop-portal-kde`
https://superuser.com/questions/1784412/problems-with-file-upload-in-chrome-based-browser-on-kde

I'm not an expert in this area, I'm lost. I hope provided info is enough to fight this bug.

SOFTWARE/OS VERSIONS
KDE Plasma Version: 5.27.6
KDE Frameworks Version: 5.107.0
Qt Version: 5.15.10

ADDITIONAL INFORMATION