Thank you so much for your answer Jakob,
I have tried all the alternatives with no success.
In fact, for the first alternative, this is what I had already done for the first time. Changed <routes xmlns:xsi="
http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="
http://sumo.dlr.de/xsd/routes_file.xsd"> to <routes> for the route file for example. The simulation ran very fast, but couldn't end, instead it throws a 139 exit code I have explained in my previous answer.
For alternative 2, I don't really know how to add this option when running sumo. In fact, I am running it with its script in the veins package in the Linux command line like this ~/src/veins-veins-4.7.1/sumo-launchd.py -vv -c /usr/bin/sumo. Maybe by running sumo with sumo-gui or sumo, I could add this option but not with the script I am using.
For alternative 3, the SUMO_HOME environment variable were already set, so nothing has changed.
The figure below shows the exact error I am getting
And when I open the link directly in my browser, I get this message "This XML file does not appear to have any style information associated with it. The document tree is shown below.
"