[Software] Qt5 file picker causes applications to crash after upgrading to 26.04

[yo5lka]

Since upgrading to Kubuntu 26.04 and KDE Plasma 6.6 (currently on 6.6.6), Qt5 applications crash when they need to open the file picker for opening/saving. Qt6 applications are not affected. Below is a crash log from Qt5 Designer, but all other Qt5 applications do the same thing when opening a file picker.

https://yo5lka.net/temp/qt5_crash.log (sorry if I wasn't supposed to post links, but I couldn't figure out how to include the log without making a huge message)

Has anyone else experienced this? I found some people with the same issue over on the Arch and Manjaro forums, but most answers from there are not applicable to the Debian/Ubuntu ecosystem.

[die.boer]

Let's 1st see whether this is specifically the Qt5 + Plasma 6 Wayland integration.
In a terminal run

QT_QPA_PLATFORM=xcb designer

then try File - Open

tell us if it works without crashing

[yo5lka]

It still crashes, unfortunately.