Welcome! This forum has a treasure trove of great info – Scouters helping Scouters! Just a heads up, though - all content, information, and opinions shared on this forum are those of the author, not the BSA.
Matt, I realize that BSA has a record of everyone who has taken YPT. To take YPT, an adult has to create a login and profile. Until my.scouting asks the question “do you have a child currently registered in Scouting” and provides drop downs indicating council name and unit type and number, I don’t see how a report listing non-registered parents can be generated.
On the other hand, it’s been such a long time since I created the my.scouting account, perhaps that question is being asked these days.
Go the other way. Every Scout has a connected parent that is associated with the unit. You would “crawl” all Scouts, their associated parents, and see if they have YPT.
There is a linkage, as Matt suggests, and a request has been made to add a parent YPT report. When a Scout is registered, the application includes a parent field, or if online, it is automatic.
I do not know if or when the report would be created and made available. Until then, the extension report is working.