Free wifi in most cafés, all McDonald's on Champs-Élysées, tons of public spaces. Download WiFi Map app — Shows passwords for networks citywide in Marais and République.

Orange tourist SIMs €20 for 20GB data at CDG airport or any Orange store. Much cheaper than international roaming for Métro navigation.

Most Métro stations have free "WIFI_RATP" now including Lines 1, 4, and 14. Slow but works for Google Maps and WhatsApp between République and Châtelet.