I installed F39 XFCE on a new machine and noticed that links do not work. After a significant amount of digging (and some help from the forum https://discussion.fedoraproject.org/t/cant-open-links-from-flatpak-applications/95614), we determined that the issue is that the XFCE spin does not have a configuration for `xdg-desktop-portal`. 

It looks like this issue has been fixed upstream with two fixes, both of which are likely required to be brought downstream.

1. Adding a portals.conf for XFCE https://gitlab.xfce.org/xfce/xfce4-session/-/blob/xfce-4.18/xfce4-session/xfce-portals.conf?ref_type=heads
2. Ensuring that XDG_* variables are populated upon login https://gitlab.xfce.org/xfce/xfce4-session/-/commit/0fe26b4d0eab7207c5349af340eb9e8cb833e29c

It seems this originates from the fact that x-d-p removed fallbacks for link handling, and now desktop environments are required to provide configurations for it. Unfortunately, even if you do add a `xfce-portals.conf`, right now the XDG_CURRENT_DESKTOP variable is not populated automatically, hence the need for the second fix

```
$ systemctl --user show-environment
HOME=/home/nick
LANG=en_US.UTF-8
LOGNAME=nick
PATH=/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin
SHELL=/usr/bin/zsh
USER=nick
XDG_DATA_DIRS=/home/nick/.local/share/flatpak/exports/share:/var/lib/flatpak/exports/share:/usr/local/share/:/u>
XDG_RUNTIME_DIR=/run/user/1000
DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus
DISPLAY=:0
XAUTHLOCALHOSTNAME=
XAUTHORITY=/run/lightdm/nick/xauthority
```

Reproducible: Always

Steps to Reproduce:
1. Open a flatpak app that has clickable links, such as Signal
2. Click the link
3. Observe nothing happens
Actual Results:  
The link does not open in my browser

Expected Results:  
The link should open in my browser