KDE apps can't start and leak memory

Problem

Since I upgraded to Debian 13, KDE apps won’t start and leak memory.
I use these apps (Dolphin, Spectacle, etc.) without the Plasma desktop.
I3 is the windows manager.
I am using proprietary Nvidia drivers.

I tried reinstalling the whole KDE suite, with and without the Plasma desktop (even if I don’t use it), nothing changes.

Dolphin :

• I start dolphin
• It issues what seems to be a harmless warning :

kf.service.sycoca: The menu spec file ( "" ) contains a Layout or DefaultLayout tag without the mandatory Merge tag inside. Please fix it.

• No window appears
• Process dolphin is now alive and starts eating memory
• It eventually gets killed after 5 minutes or so by early-oom, when the systems runs low on memory.

If interrupted by Control-C, process and leak stop and memory is freed.

Spectacle has the same behavior.

Gwenview

• I start gwenview
• It issues the previous warning along with others
• A Gwenview window appears
• It freezes immediately (I can’t click, thumbnails don’t load)
• It starts leaking memory

Gwenview, second test

• I start gwenview
• It issues the previous warning along with others
• A Dolphin (!) window appears
• It freezes and leaks memory

Krusader

Krusader works fine.
Edit: did a package upgrade today, Krusader now has same behavior as Dolphin.

Breeze icons

Icons are still used successfully by various programs. However, they appear huge, as if they couldn’t be resized.

System calls

strace dolphin reports the process infinitely calling brk()

Reset of configuration files

On my system, every /home/user/.something is a symlink to /dotfiles/user/.something on a faster drive.
So to test launching the software without .cache and .config I just removed temporarily the symlinks. Everything is indeed reset but dolphin and others still don’t start and leak memory.

Package management issues

apt seems unhappy with my system, sometimes a standard upgrade is removing software I installed : for instance qgis, showfoto or even virtualbox-7.0. So after the upgrade I ask to reinstall those packages. It works after having installed/removed some libraries.