Two months and some progress.
And some stuck points too.
I sorted out the boot order problem which prevented my main install from booting, including copying files from a newer image but not the kernel, because I wanted my compiled kernel to run with the udlfb driver.
Then tried to install the
xf86-video-displaylink driver. It won't compile on the armel platform, although it compiled for the armhf with the same xorg versions.
At this point I had the choice of a green screen or a login (slim) screen.
The system didn't respond to keyboard or mouse input.
After finding a
compiled armel driver from ubuntu I installed that with dpkg. After that I only got the green screen and no login screen - even after I'd removed the package!