Thanks anyway.
Given i have the very distinct feeling that most others who have read this thread are / might be as mystified as me about [a] what happened? ** why? [c] how to repair it? , I have now thrown in the towel & gone semi-nuclear.
I was prepared & intending today to go full-nuclear, by which i mean a complete new installation with another distro [KDE Neon], given my shock that TW would do this to my Lappy despite openQA, & despite BtrFS+Snapper+Rollbacks. However i had forgotten how poor the Neon Installer is, compared to the wonderful Ruby. It would not allow me to reuse my encrypted home partition [groan, that’s not right, is it? Um, my [i]/dev/sda5** encrypted partition on which /home is mounted; is that right?] without formatting it, thus definitely losing everything *. So i abandoned that intended Neon installation, & am currently 40’ into the following…
I rebooted Lappy with my old “openSUSE-Tumbleweed-DVD-x86_64-Snapshot20170510-Media.iso” USB stick, with which i had initially migrated both my Tower & Lappy to TW earlier this year. I configured Ruby to reformat each partition [but still in same guise as original], except /dev/sda5 encrypted partition, which i set to reuse as-is. I knew this would cause Ruby to ask me for my existing encryption password, & my hope was that Ruby would still successfully then access that partition… which it did. Hence, the TW reinstallation is now in progress; given how lousy Australian “broadband” speeds are, it will be hours before this finishes.
Obviously i’ve now lost all my programs, so i’ll need to reinstall them again later, but at least IF this semi-nuclear option succeeds in saving my current /home then under the circumstances i’ll regard this as a win. All my data is safe on backups, so that’s not the main reason i have been keen to save Lappy’s /home if at all possible… it also has some VirtualBox VMs which due to size are not able to be backed up, & i’d much prefer not to lose them.
Fingers crossed that this works. I’m not putting my Neon USB stick back in the drawer just yet…*