The operation couldn't be completed.
(com.apple.installer.pagecontroller error -1.)
(com.apple.installer.pagecontroller error -1.)
I examined the name of the package I had created. This application has an ampersand in its name, and I put its version number, 6.0, at the end of the package name. I know that the period in the version number does not cause any issues, nor do spaces in the name, so the only odd one out is the ampersand. I removed it, rebuilt the package, and found that I could install it without issue.
So, in summary, don't use an ampersand in the title of a macOS installer package, or you'll get a very unhelpful error.