The second instance is just black with the cursor whether TTY1 (the default for my system) and the subsequent TTY is using startx or startplasma-wayland.
When I do so, taking screenshots with spectacle causes the compositor to crash, and in fact, entirely reboots my machine.
Make sure to run a separate dbus session for your second plasma session
dbus-run-session startplasma-wayland
That works! Thanks, lots. I couldn’t find that method online.
Would it be reasonable to suggest at bugs.kde.org that if the same user tries to run startx or startplasma-wayland from two separate TTYs, Plasma would detect that and automatically reinvoke itself with dbus-run-session startx?
The consequences otherwise are really bad – an error shouldn’t usually cause the PC to shutdown, right?
If anyone submitted a patch to do it, we’d probably accept it, but I don’t think it’s worth tracking with a bug report as this is like in the 1% of rare use cases of the 1% rare rare cases.