xdg-desktop-portal 1.17.x introduces a new way to select which portals will
be used for which desktop environments, modelled on mimeapps.list:

- each desktop environment should provide a file like
  /usr/share/xdg-desktop-portal/mate-portals.conf

- the filename is ${DESKTOP}-portals.conf where ${DESKTOP} is the desktop
  environment's entry in $XDG_CURRENT_DESKTOP (the same as the DesktopNames
  from /usr/share/{x,wayland-}sessions/*.desktop), folded to lower case

- sysadmins and users can override this via files named portals.conf or
  ${DESKTOP}-portals.conf in various locations like /etc/xdg-desktop-portal
  and ~/.config/xdg-desktop-portal

Please see portals.conf(5) or its source code
https://github.com/flatpak/xdg-desktop-portal/blob/main/doc/portals-conf.rst
for full details.

As a backwards-compatibility mechanism, x-d-p will fall back to trying
to guess the most appropriate portals from the portals' UseIn= fields,
but it will log warnings when it does that, and anyway Debian doesn't
currently ship any portal backends that are flagged as suitable for MATE
(although I see there's an ITP open for x-d-p-xapp, #1038946). Please
add an mate-portals.conf to tell x-d-p more explicitly what backends
MATE is meant to be using by default.

For example, if the intention is to try to use the -xapp backend, falling
back to -gtk if -xapp isn't installed or doesn't know how to do something,
the way to write that would be:

[preferred]
default=xapp;gtk;

The desktop environment (either mate-session-manager or some larger
metapackage) should probably also have a Recommends, or at least a
Suggests, on whatever portals would be most appropriate for it.

Thanks,
    smcv

Control: forwarded -1 https://github.com/mate-desktop/mate-desktop/issues/574
Control: tags -1 + upstream

If this isn't fixed via an upstream change, it would be appropriate
(and quite easy) to do this as a Debian-specific change.

Thanks,
    smcv

Hi Simon,

The mate-portals.conf will be shipped in mate-desktop (providing the
libmate-desktop-* base library) starting with mate-desktop 1.26.2.
(Uploading in some minutes).

The mate-session-manager bit, I need to check deeper.

Greets,
Mike

Control: reassign -1 mate-desktop 1.26.1-1
Control: affects -1 mate-session-manager
Control: tags -1 + fixed-upstream pending

For the purposes of this bug, it doesn't matter whether mate-portals.conf
is in mate-session-manager or in one of its dependencies, as long as
installing a somewhat minimal MATE desktop will pull it in.

mate-session-manager is the package that owns
/usr/share/xsessions/mate.desktop, so ideally installing
mate-session-manager ought to provide mate-portals.conf either
directly or indirectly. m-s-m depends on mate-desktop-common, and it seems
that you added mate-portals.conf to m-d-c, so I think this bug is now
solved: reassigning to mate-desktop-common so that it can be closed as
fixed in 1.26.2-1.

Thanks,
    smcv

Es gibt eine Familienspende in Höhe von 1.850.000,00 USD von Cheng Charlie
Saephan. Bitte antworten Sie für weitere Informationen. Denken Sie daran,
Ihrer Familie und den Bedürftigen in Ihrer Umgebung Gutes zu tun.

Dies ist bereits der zweite Versuch, Sie zu erreichen. Bitte antworten Sie
für weitere Details.

Es gibt eine Familienspende in Höhe von 1.850.000,00 USD von Cheng Charlie
Saephan. Bitte antworten Sie für weitere Informationen. Denken Sie daran,
Ihrer Familie und den Bedürftigen in Ihrer Umgebung Gutes zu tun.

Dies ist bereits der zweite Versuch, Sie zu erreichen. Bitte antworten Sie
für weitere Details.