Progress, if only 1 data point: pulling calibre and calibre-bin 3.30 from raspbian/testing (as seen at
raspbian.raspberrypi.org and
archive.raspbian.org) suddenly today works, when installing onto the latest Raspbian Lite on RPi3, as follows:
I don't have high confidence this will continue to work with Calibre 3.31 later in September (as more than half of all versions since Calibre 3.22 have failed to install from raspbian/testing since May 2018, very sadly) but still let's celebrate today's positive news!