The first install I tried, this time around, was 18.04 and 1.5.7. I gave up because of the failed install of several modules during the fog install. I looked up the error messages I kept on receiving and came to this forum where several others reported the same problems. One suggestion from a user (not a developer) was that 16.04 and 1.5.2 and 1.5.0 would work.
The point is that the very particular error message I started this thread with I also got trying to install 18.04/1.5.7, but then with numerous others remaining.
But when I kept fighting through one error message after the other (with 16.04/1.5.2), I finally managed to narrow it down to this one particular message. The previous two installs in 2010 and 2013 weren’t exactly easy either, but I did get through them in the end looking up one error message after.
Trying 18.04/1.5.7 in a virtual machine this time.