The problem has been solved. It turned out that Qubes is tolerant of KDE Neon, but KDE Neon is not tolerant of Qubes. My solution was to delete both installations, install Qubes first, and KDE Neon second. Now both boot fine. So, I did it again in the reverse order, and I replicated my first problem
So... the answer was to install KDE neon on top of Qubes rather than Qubes on top of KDE neon. I have no idea why this makes a difference. -- You received this message because you are subscribed to the Google Groups "qubes-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to qubes-users+unsubscr...@googlegroups.com. To post to this group, send email to qubes-users@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/qubes-users/207e5605-efd1-414c-9a9a-8f2e5447adc5%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.