I initially reported this bug at https://discuss.kde.org/t/dolphin-paste-clipboard-content-not-working-because-of-mime-type/41297/3 and was asked to make a bug report over here.

STEPS TO REPRODUCE
1. Open a Webpage in Firefox (I used KDE’s english Wikipedia page)
2. Right click on Matthias Ettrich’s image, choose “copy image”
3. Open up Dolphin and press Ctrl+V (Dolphin displays my home directory, I have write permissions)
4. Select “JPEG image”
5. Press OK
6. Observe that no file is created

EXPECTED RESULT

The file is created correctly

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: NixOS unstable/Hyprland (also replicated on Arch Linux/COSMIC DE)
KDE Plasma Version: -
KDE Frameworks Version: 6.19.0
Qt Version: 6.10

ADDITIONAL INFORMATION

I have used this feature many times before and it worked perfectly.
Pasting a screenshot taken with grim works perfectly.

`wl-paste --list-types` output when the image is copied to the clipboard:

text/html
text/_moz_htmlinfo
text/_moz_htmlcontext
image/png
image/jpeg
image/bmp
image/x-bmp
image/x-MS-bmp
image/x-icon
image/x-ico
image/x-win-bitmap
image/vnd.microsoft.icon
application/ico
image/ico
image/icon
text/ico
image/tiff
SAVE_TARGETS

`wl-paste --list-types` output when a screenshot is taken via grim:

image/png