Debian Buster on The Optiplex 755 (USFF)

Or: (Almost) Spring Cleaning & Update
Yesterday it was time to upgrade the little monster, the Optiplex 755.
I was using a HDD of 80 GB and it a major PITA, always at 99% capacity or so; a new, or at least, a bigger HDD was in order, and, since I'm updating, bumped the thing from Stretch to Buster (not Sid because I found out that installing updates all the time it is ball breaking business).
Also, since this particular Optiplex can only handle up to 4 GB of RAM, ditched XFCE for a plain i3 solution.
Installation (64 bits, on an encrypted LVM as usual) went smooth as silk.