happy to report that the deal-breaker problem with the trackpad,
extremely frustrating, can be solved by installing a different trackpad
driver. Although I am aware that ubuntu on MacOS hardware is not the
primary focus of this list, I will record the useful command for
posterity and for those following. On this MacBook 2,1, this was the
working command:
sudo apt install xserver-xorg-input-synaptics-hwe-18.04
other versions of this command, for example:
sudo apt install xserver-xorg-input-synaptics
were not correct for this on this machine, at least.
K