Adopting a quick down-top troubleshooting strategy, it seems that the Border Radio venue was converted into a giant fucking Indian Internet point for 300+ students (it seems studying zones are closed because of COVID-19 concerns).
So a fleet of students from everywhere outside and inside the Border Radio venue is hijacking our Internet connection with dozen of pirate access points connected like bloodsuckers and... they also plugged off the cable of the Border Radio regia to make the sysadmin happy.
Holy - fucking - shit.
Connected again the cable and it works. Running away to do not kill anybody.