[Evolution] Print to File -- where does it go? (Flatpak)

[duane johnson gmail com]

When I select an email and "print" (ctrl+P), the dialog allows me to
select "Print to File" as the Printer. Once selected, there is a File
(destination) selector, and filetype selector (default PDF) below the
list of printers.

If I use the default File destination, it *says* that it is going to
save the PDF file to my home directory ("/home/duane" in my case).
That's fine, so I press the "Print" button.

However, when I visit this destination location on my drive, there is
no PDF file present.

When I investigate the file destination by clicking the selector before
printing, it's clear the destination is not *actually* my "/home/duane"
folder, even though it says that, because "/home/duane" is empty. This
appears to be a sandbox of some kind?

Where can I find the PDF file on disk?

I'm running Evolution 3.44.1 (by Flathub.org)

Thanks,
Duane Johnson