Neither will running startplasma-x11 from Xterm in an IceWM session launched from TDM, but I can't find any clues in Xorg.0.log, journal, dmesg or .xsession-errors. Attached tail from tdm.log has lots of errors, but I can't tell that any suggest Plasma errors. The openSUSE forums report problems launching Plasma Wayland, but if there are any for X11, I'm missing them.