Thank you for responding Kovid!
Perhaps I'm misunderstanding something. My understanding (per:
https://manual.calibre-ebook.com/dev...nt-environment) was that running calibre-develop -g will set the CALIBRE_DEVELOP_FROM env variable to the source directory which I'm developing from (i.e. where I've added the debugger module and execution) and then run the calibre-debug executable.
That seems to be what's happening... but the execution is erroring out on the debugpy.listen method for some reason.