After an incredible struggle, I finally managed to get my beloved to come upstairs and plug the pi in for me, putting the buts together and then finding it a suitable home with mains and wired Ethernet straight into the main switch.
After a bit of initial stupidity, couldn’t work out what the default username was, it was "pi" iirc, fired the Pi up, logged in and all was well.
I assigned it a good IPv4 address as usual via DHCP which points to a fixed routable address set by the Firebrick acting as DHCP server according to the Pi’s ethernet MAC address.
Have set usernames and passwords, usual mucking about with ‘screen’ which is mysterious to me but just does something wonderful.
Fired up gdc and built a hello world exe from minimal D source, got some nice AAarch64 (not 32-bit mode) asm source out of it with a gdc -S.
It’s a thing of beauty. Can’t thank vic0239, IanG, Johnson and other contributors enough. I’ve said this before, sincerely meant.
I know vic0239 told me he has kept a backup of the card image for me, but I ought to back the whole system up somehow, before I do too much damage.