To install xdg-desktop-portal just follow these instructions.
sudo apt-get install xdg-desktop-portal
Which will install xdg-desktop-portal and any other packages on which it depends.
|Maintainer||Utopia Maintenance Team <email@example.com>|
|Description||desktop integration portal for Flatpak possibly other desktop containment/sandboxing frameworks. This service is made available to the sandboxed application, and provides mediated D-Bus interfaces for file access, URI opening, printing and similar desktop integration features.|