jenkins stuck "Please wait while Jenkins is getting ready to work"
OK, a good week-end does its job as usual: My issue was indeed caused by my company proxy (a good thing would be to add this requirement in the jenkins doc, i might have  missed it anyway).
So the fix is actually simple, just need to add the correct options to the jenkins start command, as in:

-Dhttp.proxyHost=&lt;your_proxy_ip_here&gt; -Dhttp.proxyPort=&lt;your_proxy_port_here&gt; -Dhttps.proxyHost=&lt;your_proxy_ip_here&gt; -Dhttps.proxyPort=&lt;your_proxy_port_here&gt;


Full example:

/usr/bin/java -Djava.net.preferIPv4Stack=true -Dhttp.proxyHost=10.21.92.40 -Dhttp.proxyPort=3128 -Dhttps.proxyHost=10.21.92.40 -Dhttps.proxyPort=3128 -jar /usr/share/jenkins/jenkins.war --webroot=/var/cache/jenkins/war --httpPort=8080


tcpdump was the savior here (+ a colleague :) )