The problem is that xdg-open assumes that you have pcmanfm if you use LXDE. So if you don't have pcmanfm, it just fails and opens nothing. Instead it should fallback to the generic method.
It also assumes you have pcmanfm if you use LXQt. But the default file browser for LXQt is pcmanfm-qt (at least on archlinux)
Created attachment 131382 [details] [review]
Patch to work if pcmanfm doesn't exist in lxde or lxqt
This checks to see if pcmanfm or pcmanfm-qt exist before calling them, and falls back to using open_generic.
Created attachment 134515 [details] [review]
I've hit same bug with xdg-utils-1.1.2. Patch worked for me, but I've updated it a bit.
LXQt can be installed without pcmanfm-qt. IMO https://github.com/luis-pereira/xdg-utils/commit/dbf58e9fd8c5e2089a13522d87d2e660e159b8e2 is a better fix.
Upstream bug report: https://github.com/lxde/lxqt/issues/1298
Created attachment 136325 [details] [review]
xdg-open fix for LXQt
please, consider the attached patch, which makes xdg-open usable again in LXQt.
*** Bug 103146 has been marked as a duplicate of this bug. ***
Thanks for the patch, applied