Created attachment 166929 [details]
Falkon browser at 150% display scale

SUMMARY

This happens after upgrading to KDE6.  I set my monitor to 150% scale.  But the web content I see in the Falkon browser seems to be zoomed badly, with text and image edges with uneven widths, as if it were zoomed using near-neighbour interpolation.

STEPS TO REPRODUCE
1. Open System Settings, go to "Display & Monitor", and set "Scale" to 150%
2. Open the Falkon browser
3. Open any web page (such as the default page https://www.falkon.org/)

OBSERVED RESULT

See the attached screenshot.  Characters are badly shaped, with unevenly thick and thin strokes.  The image is also a bit blurred. 

EXPECTED RESULT

The text should have sharp edges, and the image should not be that blurred.

SOFTWARE/OS VERSIONS
Operating System: Arch Linux 
KDE Plasma Version: 6.0.1
KDE Frameworks Version: 6.0.0
Qt Version: 6.6.2
Kernel Version: 6.7.9-arch1-1 (64-bit)
Graphics Platform: Wayland

ADDITIONAL INFORMATION

If I set "Scale" to 100%, the problem disappears.

This same problem also appears in the Angelfish browser.

This problem does not appear in the Firefox browser (running natively as a Wayland client) even if the "Scale" is set at 150%.

I am using the Plasma Wayland session.  If I invoke "falkon --platform xcb" on the command line, the text looks smoother.  But I am not sure whether it is aware of HiDPI and therefore renders directly at higher resolution, or it uses a smoother scaling algorithm.