Для начала нужно включить вывод подробных сообщений об ошибках с помощью:

kdebugdialog

А затем смотреть сообщения в ~/.xsession-errors:

tail -f ~/.xsession-errors

После нескольких подряд сворачиваний-разворачиваний окна konsole kade plasma-shell падает.

Aug 11 10:37:02 mike-swift plasmashell[22457]: XMLHttpRequest: Using GET on a local file is dangerous and will be disabled by default in a future Qt version.Set QML_XHR_ALLOW_FILE_READ to 1 if you wish to continue using this feature.
Aug 11 10:37:02 mike-swift plasmashell[22457]: XMLHttpRequest: Using GET on a local file is dangerous and will be disabled by default in a future Qt version.Set QML_XHR_ALLOW_FILE_READ to 1 if you wish to continue using this feature.
Aug 11 10:37:02 mike-swift plasmashell[22457]: malloc(): unsorted double linked list corrupted
Aug 11 10:37:05 mike-swift systemd[2814]: plasma-plasmashell.service: Main process exited, code=killed, status=14/ALRM
Aug 11 10:37:05 mike-swift systemd[2814]: plasma-plasmashell.service: Failed with result 'signal'.
Aug 11 10:37:05 mike-swift systemd[2814]: plasma-plasmashell.service: Consumed 1.888s CPU time.
Aug 11 10:37:05 mike-swift kwin_x11[3175]: qt.qpa.xcb: QXcbConnection: XCB error: 3 (BadWindow), sequence: 62612, resource id: 25165853, major code: 15 (QueryTree), minor code: 0
Aug 11 10:37:05 mike-swift kwin_x11[3175]: qt.qpa.xcb: QXcbConnection: XCB error: 3 (BadWindow), sequence: 62685, resource id: 25165884, major code: 15 (QueryTree), minor code: 0
Aug 11 10:37:06 mike-swift systemd[2814]: plasma-plasmashell.service: Scheduled restart job, restart counter is at 9.
Aug 11 10:37:06 mike-swift systemd[2814]: Stopped plasma-plasmashell.service - KDE Plasma Workspace.
Aug 11 10:37:06 mike-swift systemd[2814]: plasma-plasmashell.service: Consumed 1.888s CPU time.
Aug 11 10:37:06 mike-swift systemd[2814]: plasma-plasmashell.service: Start request repeated too quickly.
Aug 11 10:37:06 mike-swift systemd[2814]: plasma-plasmashell.service: Failed with result 'signal'.
Aug 11 10:37:06 mike-swift systemd[2814]: Failed to start plasma-plasmashell.service - KDE Plasma Workspace.

Дело оказалось в новом ядре, (6.4.9), после отката на 6.2.0 - все нормализовалось.