This is either a defect with xdg-desktop-portal 1.18.0 or with Steam and I suspect the latter. Downgrading xdg-desktop-portal to 1.16.0 resolves the issue and the file picker opens normally.

This is either a defect with xdg-desktop-portal 1.18.0 or with Steam and I suspect the latter. Downgrading xdg-desktop-portal to 1.16.0 resolves the issue and the file picker opens normally.

I can confirm the fix as well. The following was done on Arch Linux:

sudo pacman -U https://archive.archlinux.org/packages/x/xdg-desktop-portal/xdg-desktop-portal-1.16.0-1-x86_64.pkg.tar.zst
sudo pacman -Rs xdg-desktop-portal-gtk xdg-desktop-portal-gnome xdg-desktop-portal-gtk

This resulted in a a functioning popup of the FilePicker and a popup as expected. I do, however see, the Steam window doesn't handle closing the FilePicker correctly, and will print out #ContentManagement_Error_ on the "Add a new Steam library folder" popup:

I had the same issue on an ArchLinux fresh install with the i3 WM and xdg-desktop-portal 1.18, started with startx (no lightdm, gdm)

The following commands were executed to fix that :

pacman -Qqs xdg-desktop-portal | sort -r | sudo pacman -R -
# Remove any xdg-desktop-portal package

sudo pacman -U https://archive.archlinux.org/packages/x/xdg-desktop-portal/xdg-desktop-portal-1.16.0-1-x86_64.pkg.tar.zst
# Reinstall xdg-desktop-portal and select xdg-desktop-portal-gtk (3) (!IMPORTANT)

sudo sed -in '/UseIn/s/$/;i3/' /usr/share/xdg-desktop-portal/portals/gtk.portal
# Add "i3" to the "UseIn" section of the gtk portal definition

# Assert that you have set the DISPLAY and XDG_CURRENT_DESKTOP environment variables set
echo $DISPLAY
echo $XDG_CURRENT_DESKTOP

# If DISPLAY is not set, you should start X
# If XDG_CURRENT_DESKTOP is not set, you should set it (I use 'dex' in my i3 autostart script)

systemctl --user import-enviroment DISPLAY XDG_CURRENT_DESKTOP
# Import the enviroment variables in systemd

systemctl --user daemon-reload
systemctl --user restart xdg-desktop-portal xdg-desktop-portal-gtk
# Restart the xdg-desktop-portal services

systemctl --user status  xdg-desktop-portal xdg-desktop-portal-gtk
# Check that there was no error on service startup

# Launch steam and add a library folder!

Note that this is a temporary fix, we should report this to the ArchLinux maintainers.

For myself, running KDE Plasma on Arch Linux, the following fixed my issue with Steam FileChooser.

1. I started the xdg-desktop-portal service, as it wasn't running.
   systemctl start --user xdg-desktop-portal
2. I installed xdg-desktop-portal-kde, as it wasn't installed.
   pacman -S xdg-desktop-portal-kde
3. I rebooted my PC.
4. Now it is working.

I am running the following versions of xdg:

• xdg-desktop-portal 1.18.0-2
• xdg-desktop-portal-kde 5.27.9-1

XDG-Portals is now happy in Steam:

  "xdg-portals" : {
    "details" : {
      "interfaces" : {
        "org.freedesktop.portal.Email" : {
          "available" : true,
          "version" : 4
        },
        "org.freedesktop.portal.FileChooser" : {
          "available" : true,
          "version" : 3
        },
        "org.freedesktop.portal.Inhibit" : {
          "available" : true,
          "version" : 3
        },
        "org.freedesktop.portal.OpenURI" : {
          "available" : true,
          "version" : 3
        },
        "org.freedesktop.portal.ScreenCast" : {
          "available" : true,
          "version" : 5
        },
        "org.freedesktop.portal.Settings" : {
          "available" : true,
          "version" : 2
        }
      },
      "backends" : {
        "org.freedesktop.impl.portal.desktop.gtk" : {
          "available" : false
        },
        "org.freedesktop.impl.portal.desktop.kde" : {
          "available" : true
        }
      }
    },
    "issues" : [
    ]

I am facing the same problem and I see only installation destination screen and can't choose folder.
I installed xdg-desktop-portal-gtk.

And I only see this error>
"The 'version' property is not available for 'org.freedesktop.portal.ScreenCast', either there isn't a working xdg-desktop-portal or it is a very old version",

I think this error should not impact file chooser. Can you please help me how to fix the problem?

Edit: I am working on ubuntu-20.04

I have the same problem on Nobara, fork of Fedora.
Issue applies both to the Nobara repo version and flatpak one.
Has anyone managed to deal with the issue there?

In the recent beta update, the issue of "unpopulated" folder trees has been fixed, but one last problem remains:

1. Go to the "Steam settings" -> "In Game"
2. "External screenshots folder" -> "Choose folder": a new window opens: "Select external screenshots folder"
3. At first this seems to be fully functional, you can browse to any filesystem location.
4. Choosing "Select", however, leads to an immediate crash, no matter which folder is chosen.
   No error messages or further log entries can be seen.

On my machine, this happens everywhere where the fallback file picker is used: as soon as I click on select after choosing a folder from the directory tree, the steam client crashes immediately.