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### Problem description
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implemented, or link to an existing issue describing it -->
see #723
### Implementation description
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`xdg-desktop-portal-wlr` is not relevant because it does not provide the
FileChooser interface.
`xdg-desktop-portal` needs the `WAYLAND_DISPLAY` env var on wayland and
the `DISPLAY` and `XAUTHORITY` env vars on xorg. If the dbus user
session bus is not run in a way that it already gets those variables,
they must be given via `dbus-update-activation-environment(1)`.
### Screenshots
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make before/after sceenshots -->
### Additional things
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fixes#723
d9a4906b3c