French side has fiber optic internet at most places now it seems, at least orient beach and such. Was strong enough to stream/skype/video calls if needed. Sometimes Airbnb will say if they have strong Wi-Fi in description.
https://www.airbnb.com/rooms/53771079?source_impression_id=p3_1644180476_94s49fzoZRZ%2F5ZiW
like this place says Wi-Fi 100Mbps, so pretty fast