As an aside, I did figure out why my filesystem permission override wasn't working with FF – the override only worked when set with `sudo` and not on the user installation. The `flatpak info --show-permissions` output merges them, which is pretty misleading.
I think the best user experience currently achievable is just to always default to the configured download directory and not the last one, at least if it's a portal directory.
As an aside, I did figure out why my filesystem permission override wasn't working with FF – the override only worked when set with `sudo` and not on the user installation. The `flatpak info --show-permissions` output merges them, which is pretty misleading.
I think the best user experience currently achievable is just to always default to the configured download directory and not the last one, at least if it's a portal directory.