Tip: Use this command to batch-set all your installed GNOME Runtime-based Flatpak apps which don't yet use portallized Open/Save dialogs to default to opening the dialog to $PWD instead of the Recent tab.
for X in $(flatpak list --app-runtime=org.gnome.Platform --columns=application | tail +1); do flatpak run --command="gsettings" "$X" set org.gtk.Settings.FileChooser startup-mode cwd; done