Here is a recording of the issue, can't reproduce on Wayland
Pretty sure this is not a 5.26.90 breakage as I've seen it before, but thought it was caused by kwin-forceblur script.
It turns out that if Konsole's blur option is disabled, blurs are is still shown due to LightlyShaders being enabled (?), and if force-blur is enabled with "Blur only the content of window" it will update the blur region on window size changes making this bug go unnoticed
Here is a recording of the issue, can't reproduce on Wayland
Pretty sure this is not a 5.26.90 breakage as I've seen it before, but thought it was caused by kwin-forceblur script.
It turns out that if Konsole's blur option is disabled, blurs are is still shown due to LightlyShaders being enabled (?), and if force-blur is enabled with "Blur only the content of window" it will update the blur region on window size changes making this bug go unnoticed
https://user-images.githubusercontent.com/15076387/213956600-8705c0c1-8684-4538-b5b8-656bc59ff136.mp4
System details: Operating System: Arch Linux KDE Plasma Version: 5.26.90 KDE Frameworks Version: 5.102.0 Qt Version: 5.15.8 Kernel Version: 6.1.7-arch1-1 (64-bit) Graphics Platform: X11 Graphics Processor: Mesa Intel® UHD Graphics 630