Eduroam is an Internet access service for academics. In most universities and research center, there is a WiFi Eduroam one can connect to for free.
First, you need to sign up, with “annuaire UPMC” credentials. There is no need to be within the campus to sign up, you can sign up while you're traveling.
For Mac/Windows/Linux:
For iPhone/Android, there is a similar procedure, but it didn't work on my Android 9 (Max, 06/07/2019).