It should be noted arch (which we support) doesn't create the Downloads directory by default, nor does it set XDG_DOWNLOAD_DIR.

Ubuntu doesn't set $XDG_CACHE_HOME:

$ env | grep -i xdg
XDG_CONFIG_DIRS=/etc/xdg/xdg-ubuntu:/etc/xdg
XDG_MENU_PREFIX=gnome-
XDG_SESSION_DESKTOP=ubuntu
XDG_SESSION_TYPE=wayland
XDG_CURRENT_DESKTOP=ubuntu:GNOME
XDG_SESSION_CLASS=user
XDG_RUNTIME_DIR=/run/user/1000
XDG_DATA_DIRS=/usr/share/ubuntu:/usr/share/gnome:/home/nate/.local/share/flatpak/exports/share:/var/lib/flatpak/exports/share:/usr/local/share/:/usr/share/:/var/lib/snapd/desktop

But we could fall back to $HOME/.cache.

The historical reason for using ~/Downloads (from my perspective, anyway), is that it has allowed a naïve user to pre-download the necessary parts using their browser at a time and place where the internet is more performant, then later perform the installation with a more limited (in speed or affordability) connection. This was more useful when the only external download was the Logos offline installer. Now we have that, plus the appimage, plus ICU files, and who knows what else down the road. So I agree that it makes good sense to check both locations for the necessary files, then, if we download them, put them in $HOME/.cache instead of ~/Downloads.

I assume this would actually place files into $HOME/.cache/FaithLife-Community, right?

I assume this would actually place files into $HOME/.cache/FaithLife-Community, right?

Correct, we'd want to put it in there. Logic something like:

f"{os.getenv("XDG_CACHE_HOME", "~/.cache")}/FaithLife-Community"