Well, you will forgive me if I link my Github post here anyways for posterity where I intend to explain what is in fact an issue with the way Virtualdub sets up new systems with the Wizard:
https://github.com/virtualmin/virtualmin-gpl/issues/578
I’m going to be posting there, for anyone reading this thread in the future. There is a solution to this issue. The catch all is now working fine for me.