Thanks for your input. Here’s where we are at so far.
Cannot copy any file to external SSD, nor create a folder in it. Test file had all permissions set to read and write for all.
SSD shows in GUI when attaching through USBvm to backup VM. Previously has not shown, but did after system reboot + device insert after boot. Probably also shows up fine when inserted before laptop boot, but i’d hope to be able to plug in storage for backups on the fly without having to reboot entire laptop, so that’s how i’m testing it. Qubes documentation doesn’t suggest to do otherwise.
First round of attempts all via GUI, no terminal inputs.
On inserting device to USB port, USBvm shows 3 new items in devices widget. 2 under block devices, one under USB devices. Block devices show usb/sda unnamed () with full hard drive capacity, and the second, usb/sda1 named (backups), also showing max hard-drive capacity (just a quirk of empty disk space and partitioning surely). Attaching either Sda or Sda1 shows the (backups) partition, which makes sense, as that’s the only partition on Sda. (Retrospective note for future readers: see comments below on specificity and accuracy, I made this really difficult to understand and didn’t provide correct information).
USB device shown is the brand name of the Sata-USB device I am using, which i find disconcerting, should I? Should a cable have its own identity?
VM reboot between attempts to provide fresh state, as unmounted device still shows sometimes in ‘other locations’ even after removal via widget and unmounting in VM, although it is not functional. Only noticable difference this has is on naming of next attached iteration of same mass storage, but seemingly irrelevant as things are named on the fly only for purposes of navigation and use in that vm session and attempted use of the umounted iteration would have no result. Does order of removal matter between vm and widget when trying to clear unmounted iteration? Does it even matter?
Backup VM sometimes stalls on shutdown, pop up window reads, ‘failed to shutdown after 60 seconds’, so forced shutdown, possibly due to user error in unmounting process.
Attaching the USB cable device itself to backups vm shows pop-up notifications in Dom0 of removal of mass storage devices entirely. Probably unsurprisingly, attaching of the USB device (USB-Sata cable) to backups vm does not show any storage device in GUI of backups vm.
Have not tried terminal approaches yet. Possibly i’ve conked my SSD through my unguided use of shred and gparted?
Any thoughts on whats next? Terminal commands or SSD shred and partition again? Or something else?