One last post.

The setup2hd script & subsequent update actually screwed up Multilib, because I had the 64bit only versions of aaa_libs, gcc-* & glibc-*. Now I replaced them with the latest Multilib version, and wine is up & running again. The compat32 packages have evidently been breeding like rabbits - have you seen the number of them?

I don't think that setup2hd can screw up multilib.
According to docs, setup2hd will install the squashsfs modules that together make the Live ISO, and nothing more gets installed than that.
If you have a liveslak USB stick and used the pkgtools to install multilib afterwards, and then ran setup2hd script, your computer will still only get the original squashfs modules and will see nothing of your post-installed multilib.
You would have to install all of that again on the computer harddisk installation afterwards.

When these tings happen to me (about once every 12 years or so) I take an extra backup of all of my critical data, reload a new distribution of Linux, restore my data and get on with life.

Correct. But if one has added extra squashfs modules from liveslak's /bonus directory to one's ISO (multilib, wine, nvidia...) those additions will be part of the setup2hd install.

Indeed, but I don't think that that was how the OP did it. Again, setup2hd cannot 'screw up multilib'. The user can.

As the user, I think setup2hd installed Multilib OK. Before I got to finishing the setup2hd script, I was turfed out for some reason, and that's when things began to go funny. The basic setup files like /etc/fstab weren't created. So I was getting this weird "/sbin/e2fsck is a directory" error when I tried to boot the system.

In an attempt to sort that, I upgraded current and overwrote among other things, the Multilib versions of aaa_libs, Glibc & Gcc.Then I copped on, and started untangling myself. Experience teaches you to recognize a mistake when you've made it again, as BSD fortunes assures me . I didn't have ld-linux.so in 32bit. So I reinstalled the aaa_libs, glibc & gcc from the latest current.

EDIT: Multilib-current, that is.

To do is upgrading the rest of current Multilib, as I don't want version issues arising. My LiveSlack versions are three months older than the install. Not I actually don't think I need the rest of Multilib at all, because I'm not compiling 32bit stuff.I have enough to run wine, which is all that I want. And the one library that I use wine for isn't demanding.

Anyhow, when you give yourself a clean / and a clean homedir, it's a shock to the system.Some stuff will selectively go back in, but I imagine I'll clean out a lot of junk this way.

Did you run /var/log/setup/xwmconfig or copy the right xinitrc or xsession to ~/.xinitrc & ~/.xsession ?

No, I didn't. I fingered my old /etc/X11/ as a problem. But I could pinch /etc/fstab, /etc/HOSTNAME, etc. Anyhow this box is going nicely, that half-assed window manager is gone (windowmaker)and I'm polishing the settings in small doses.

What happens is that the login stage, I can choose Mate or xfce under sddm. It remembers my choice.