Comment 19 for bug 2036098

The problem appears to have been the "DesktopNames=Lubuntu;LXQt;" line in /usr/share/xdg-desktop-portal/lxqt-portals.conf. "Lubuntu;" looks like it was causing XDG_CURRENT_DESKTOP to become "Lubuntu" in the xdg-desktop-portal process and breaking the portal.

A workaround for now is to run "sudo killall xdg-desktop-portal" after logging in - this fixes the issue for the current session (as confirmed by me and guiverc doing a ton of debugging). (sudo may be unnecessary in this command, but we didn't test without it.) Once xdg-desktop-portal is forced to restart, it picks up the right XDG_CURRENT_DESKTOP and things work. IMO this is enough for the beta to be unblocked - we have a one-liner that fixes it and we can fix this before final release by fixing the lxqt-portals.conf file.