On my up to date Fedora 34, I create a new user, start a Gnome on Xorg session, and run yakuake 21.04.1. I immediately get a coredump. Attached are the coredump and the backtraces.
Created attachment 138833 [details] coredump and backtrace (in 7za format because otherwise didn't fit the size limit)
I couldn't reproduce this bug report on my system ( compiled from master branch ) ( probably fixed on master branch while porting away from old deprecated parts)