niri / debian / flatpak unable to open save dialog

 Create or edit your portal override config at ~/.config/xdg-desktop-portal/niri-portals.conf (or globally at /usr/share/xdg-desktop-portal/niri-portals.conf):

ini

[preferred]
default=gnome
org.freedesktop.impl.portal.FileChooser=gtk

systemctl --user restart xdg-desktop-portal

https://www.reddit.com/r/voidlinux/comments/1kd642t/desktop_portal_problems_on_shady_waylands/