In any case getting the L5 to talk to my linux desktop is now moot; I found a USB doc that lets me plug in an SD card, to say nothing of actually editing files with more than 20 columns of text. It’s a bit flaky with respect to the card, and the L5 can’t charge through it faster than the battery drains, but it does work.
So no need to move files back and forth between systems to edit them.
I do have to unplug the L5 from the dock to see the effect of my changes (to the virtual keyboard), but that’s fairly painless.