Description:
Hi,

Here is a always reproductible one that I've found :

On my Debian Sid GNOME-Wayland system, I've started to try the experimental function from GNOME 3.34 (I'm running GNOME 3.34.2) that allows Xwayland to start on demand :
$ gsettings set org.gnome.mutter experimental-features "['autostart-xwayland']"
(see https://www.phoronix.com/scan.php?page=news_item&px=GNOME-3.34-Mutter-X-On-Demand)

Here what I've noticed :
- As long as XWayland is not running, LibreOffice-Flatpak doesn't start.
- As soon as XWayland is running, LibreOffice-Flatpak can be started.
- Launch LibreOffice-Flatpak and then later start XWayland : LibreOffice-Flatpak finally appears on my desktop.

By comparison, LibreOffice deb package from Debian repos can start without Xwayland.

How I've tested :
I've checked that my system starts without Xwayland by checking my processes
To start Xwayland, I've launched an X11-application (like Thunderbird or Firefox from Debian repos) which consequently starts Xwayland which consequently allow LibreOffice to start.
I've checked that Xwayland was running by checking my processes.

I'm running LibreOffice-Flatpak up to date from FlatHub :
Version : 6.4.2.2
Build ID : 4e471d8c02c9c90f512f7f9ead8875b57fcb1ec3
Threads CPU : 4; OS : Linux 5.4; UI Render : par défaut; VCL: gtk3; 
Flatpak
Locale : fr-FR (fr_FR.UTF-8); Langue IHM : fr-FR
Calc: threaded

Thanks

Steps to Reproduce:
1. Configure Xwayland on GNOME 3.34 to only start on demand
2. Launch LibreOffice
3.

Actual Results:
LibreOffice doesn't start

Expected Results:
LibreOffice should start


Reproducible: Always


User Profile Reset: No



Additional Info:
Launch LibreOffice then start Xwayland and notice that LibreOffice finally appears