Dear Maintainer, I noticed unacceptable performance and 100% CPU utilization when just typing symbols in konsole 26.04.0. For me it instantly became unusable. When I downgraded konsole to 4:25.04.2-1 everything back to normal.
(Not the maintainer.) I also noticed this, and the performance issue was so noticeable that after reading this report, and trying the workarounds in the above mentioned upstream bug report, I also went back to the previous version. I think the above is the equivalent upstream bug report, and although I tried to set QT_WIDGETS_RHI=1, that didn't seem to make a difference for me. If the upstream report does not look really the same, please just mark this as not forwarded. Thanks, Guillem