There are two possible reasons: 1. Firefox or no other browser is installed 2. Firefox or another browser is installed, but xdg-open fails to open it.
Assuming it is point 2, I re-assign this ticket to xdg-utils which provides /usr/bin/xdg-open.
There are two possible reasons:
1. Firefox or no other browser is installed
2. Firefox or another browser is installed, but xdg-open fails to open it.
Assuming it is point 2, I re-assign this ticket to xdg-utils which provides /usr/bin/xdg-open.