xdg-desktop-portal-lxqt isn't automatically started by xdg-desktop-portal on
login, so the LXQt file dialog isn't picked up by apps that could use it, like
Firefox.

Steps to reproduce:
Log in to LXQt
check running processes, such as in qps
check file dialog in Firefox with widget.use-xdg-desktop-portal.file-picker set
to 1

Actual result:
x-d-p is running, but not x-d-p-lxqt
no file dialog opens in Firefox (Unless another portal backend is also
installed)

Expected result:
x-d-p-lxqt is running
LXQt file dialog is used by Firefox


System:
Tumbleweed 20240613 and earlier, as long as LXQt 2.0.0 has been available
LXQt 2.0.0
xdg-desktop-portal-lxqt 1.0.2
xdg-desktop-portal 1.18.4
Qt 6.7.1

Workaround:
If I run /usr/libexec/xdg-desktop-portal --replace after login, x-d-p correctly
picks up x-d-p-lxqt and everything works correctly. Adding this to autostart
apps also works correctly. 

So if it's an upstream issue, openSUSE might consider adding this to packaging
temporarily as a workaround. I don't know what the underlying problem might be.