Thank you, Jeff and others!
Yesterday, I was able to download the Mac versions of Illustrator and Photoshop that were provided in a link in a previous post (thank you). The installers did install Creative Cloud, and it did try to update the CC app with the 4.5.0.331 version, but that failed. Curiously, instead of an Error Code of 1001, it was an error code 1004, which I don't think that I'd seen before.
Ivor
Ivor, thank you for the update.
For everyone currently affected by Error 1001, while installing the Creative Cloud desktop app, on macOS 10.11.6, please see "Failed to install" error received when installing Adobe Creative Cloud desktop app for an updated version of the Creative Cloud desktop app that will address this error.
Please update this discussion if you have any questions or face additional errors when applying the update.