I am running Ubuntu 16.04 and using a mobile broadband Internet connection over a Nokia E51 cellphone. Now the phone died and I wanted to get another dumb phone (no smartphone!). But I don't know how to figure out what is needed in the phone to be working as a modem? Specifically I am looking at the Nokia 3310 3g.
First of all i'm not sure if nokia3310 3g can be used as a modem. And there are 3 ways to use it as a modem a. via usb cable, b. via wifi if the phone supports wifi hotspot, c. via bluetooth tethering if supported. The only way to use this phone as a modem is via usb cable as i'm not sure that supports wifi hotspot or bluetooth tethering. You rather should check phone's manual or contact nokia.
But why don't you buy a usb mobile modem (3g/4g dongle) from your mobile provider? It's the best solution especially now that 3g/ 4g speeds are sometimes faster than adsl.