Created attachment 171523 [details]
gdb.txt run and backtrace log

plasma-workspace git f7ee03d065b4e293746248f749a7965c4321b1cb "Refactor floating panels" is the culprit -- the immediately previous e818368c22d8af554f9173fda2049439f73ab71a was both my previously working HEAD and is reconfirmed to run without segfault after a rebuild.

I'm on wayland (no X but xwayland installed), running live-git frameworks/plasma/most-gear, updated yesterday, with the segfault bisecting to the above specific commit.

100% Reproducing bisecter:
Attempted to start kde/plasma from the framebuffer login (no *DM gui login if it matters), plasmashell crashed but I got the rest of a usable session so could attempt a relaunch using krunner/konsole/whatever, only to have plasmashell crash again.  I then ultimately did the bisect and unstripped-ggdb rebuilds and ran gdb from konsole.

I should mention that I have multi-monitors; it's possible the segfault wouldn't trigger on single-monitor.

The platform is Gentoo Linux ~amd64 running the live-git kde packages from the gentoo/kde overlay.  qt 6.7.2, frameworks reporting 6.4.0 but of course it's live-git.  plasmashell --version (run in konsole) reports 6.1.80, but of course live-git as well.  I'm building with gcc-14.1.1-p20240622 p2.

I am by /no/ means a debugging/gdb expert but I rebuilt plasma-workspace (and thus plasmashell) unstripped, -ggdb, then ran gdb plasmashell, enabled logging, ran it for the segfault, did a thread apply all backtrace, detached and quit.  I'm attaching that log; hope it helps.