Running MicroOS Desktop KDE snapshot 20230330 (originally 20230212).
Proprietary nvidia drivers and wayland. My install comes automatically with
multiple xdg-desktop-portal backends: xdg-desktop-portal-gnome,
xdg-desktop-portal-kde and xdg-desktop-portal-gtk.

The problem is that the GNOME backend is started first and it times out and
fails. I think that this delays the start of xdg-desktop-portal and flatpak
applications like Firefox won't start during the delay. The portal service is
able to start after the timeout and everything works normally after that.

This github issue might be related:
https://github.com/flatpak/xdg-desktop-portal/issues/656

I tested installing a fresh MicroOS Desktop 20230330 with both GNOME and KDE
flavors. They only had the their respective backends installed with no flatpak
application launch delays on startup. My other MicroOS Desktop KDE is
originally from snapshot 20230212 so that might have had the GNOME
implementation included from the start. I'm not sure if multiple
xdg-desktop-portal implementations should even be installed in the first place
but in this state the system will have a consistent timeout with every boot.