Upon further review it appears as though the lack of a formally “registered” (for lack of a better term) datasource in Lucee Server Admin is what is causing the issue. For example, simply creating a dummy datasource with a name, and adding a “name” property to the above mentioned struct with the same name used in Admin when creating the datasource stops the error.
It seems as though there is now a dependency on first needing to register a datasource via admin, whereas previously this wasn’t the case.
This post - How to encrypt passwords - #11 by andoradmiraal - seems to suggest this was / is possible.