Can't launch steam

Hello,

I tried to launch steam, but nothing happened. Launching with console gave me this:

```
stem@stem-kubuntu:~$ flatpak run --branch=stable --arch=x86_64 --command=/app/bin/steam --file-forwarding com.valvesoftware.Steam @@u %U @@
INFO:root:https://github.com/flathub/com.valvesoftware.Steam/wiki
INFO:root:Will set XDG dirs prefix to /home/stem/.var/app/com.valvesoftware.Steam
DEBUG:root:Checking input devices permissions
WARNING:root:Missing permissions for input devices
INFO:root:Overriding TZ to Europe/Brussels
stem@stem-kubuntu:~$
```

With the verbose option

```
stem@stem-kubuntu:~$ flatpak run -v --branch=stable --arch=x86_64 --command=/app/bin/steam --file-forwarding com.valvesoftware.Steam @@u %U @@
F: No installations directory in /etc/flatpak/installations.d. Skipping
F: Opening system flatpak installation at path /var/lib/flatpak
F: Opening user flatpak installation at path /home/stem/.local/share/flatpak
F: Opening user flatpak installation at path /home/stem/.local/share/flatpak
F: Opening system flatpak installation at path /var/lib/flatpak
F: Opening user flatpak installation at path /home/stem/.local/share/flatpak
F: Opening system flatpak installation at path /var/lib/flatpak
F: /lib32 does not exist in runtime
F: Cleaning up unused container id 4292668262
F: Allocated instance id 1059569202
F: Add defaults in dir /com/valvesoftware/Steam/
F: Add locks in dir /com/valvesoftware/Steam/
F: Not sharing "/media/stem/4b656c3d-c218-4431-b1da-7693e4d9cfd6/stem" with sandbox: Unable to open path "/media/stem/4b656c3d-c218-4431-b1da-7693e4d9cfd6/stem": No such file or directory
F: Allowing wayland access
F: Allowing x11 access
F: Allowing pulseaudio access
F: Pulseaudio user configuration file '/home/stem/.config/pulse/client.conf': Error opening file /home/stem/.config/pulse/client.conf: No such file or directory
F: Running 'bwrap --args 81 -- xdg-dbus-proxy --args=80'
F: Running 'bwrap --args 79 -- /app/bin/steam '%U''
INFO:root:https://github.com/flathub/com.valvesoftware.Steam/wiki
INFO:root:Will set XDG dirs prefix to /home/stem/.var/app/com.valvesoftware.Steam
DEBUG:root:Checking input devices permissions
WARNING:root:Missing permissions for input devices
INFO:root:Overriding TZ to Europe/Brussels
stem@stem-kubuntu:~$
```

Start by rerunning the provided `flatpak run` command and its verbose variant on Kubuntu, then inspect the reported input-device permissions, missing media path, and Steam startup output. Done means the Steam Flatpak launches successfully instead of returning immediately to the shell.

Written by the indexing model from the issue text.