Hmm, after updating to the newest KDE Plasma release, plasmashell seems to no longer open. (Edit 2!: Switching back to Manjaro testing temporarily fixed this issue for me.)
I can’t seem to find any bug reports for my issue on the KDE bugtracker, possibly this is a Manjaro issue?
(EDIT: Added, KDE Bug ID 505670 )
https://bugs.kde.org/show_bug.cgi?id=505670
Shortened KDE Backtrace, for those searching;
Thread 1 "plasmashell" received signal SIGSEGV, Segmentation fault.
0x00007ffff6a9dda2 in QSGSoftwareRenderableNode::update (this=0x55555928f170) at /usr/src/debug/qt6-declarative/qtdeclarative/src/quick/scenegraph/adaptations/software/qsgsoftwarerenderablenode.cpp:151
151 if (!m_handle.simpleImageNode->texture()->hasAlphaChannel())
(gdb) backtrace
#0 0x00007ffff6a9dda2 in QSGSoftwareRenderableNode::update (this=0x55555928f170) at /usr/src/debug/qt6-declarative/qtdeclarative/src/quick/scenegraph/adaptations/software/qsgsoftwarerenderablenode.cpp:151
#1 0x00007ffff6aad820 in QSGSoftwareRenderableNode::setTransform (this=0x55555928f170, transform=...) at /usr/src/debug/qt6-declarative/qtdeclarative/src/quick/scenegraph/adaptations/software/qsgsoftwarerenderablenode.cpp:332
#2 QSGSoftwareRenderableNode::setTransform (this=0x55555928f170, transform=...) at /usr/src/debug/qt6-declarative/qtdeclarative/src/quick/scenegraph/adaptations/software/qsgsoftwarerenderablenode.cpp:327
mod edit to directly link to mentioned kde bug