To be able to connect to LTE networks you, in most regions, need your hardware AND firmware to be approved by your local radio communications authority (e.g. FC

To be able to connect to LTE networks you, in most regions, need your hardware AND firmware to be approved by your local radio communications authority (e.g. FCC). Open source baseband firmware and hardware projects exist but, even if a LTE baseband firmware and hardware were to be developed, you wouldn't be able to use it outside of a Faraday cage unless you spend lots of money getting it certified.