Yes, attempt number IV died in the now-usual fashion: inability to boot.
So for attempt number V a more-cautious approach – add one additional software package at a time, trying to isolate which, if any, is the cause of the failure.
What has occurred in the past attempts is a slow reboot, followed by an even slower one, followed eventually by the boot process failing and dropping off into busybox. I am not skilled enough to trouble shoot why this has happened. But, since the process occurs within a half-dozen or so reboots, and within the first 72 hours, I am not particularly invested in the installation so I am willing to just wipe the drive again.
So far I have installed GNUCash, Tor Browser, KeepassXC, and most recently Signal messaging desktop client, using four different methods of installation. Time to reboot again.