apparently not for SMETS2
https://www.smartenergygb.org/faqs/how-do-smart-meters-work#:~:text=No.,is solely for smart meters.
Do I need a broadband connection in my home to have a smart meter?
No. Smart meters use an entirely separate, bespoke wireless system. You don't need Wi-Fi in your home for it to work and it won't use your Wi-Fi if you have it. Your smart meter and in-home display communicate via a secure national network which is solely for smart meters. This works in the same way as other wireless systems like car remote keys or TVs, using radio waves.
Can I still get a smart meter if my home has poor mobile signal?
If you live in an area with poor mobile telephone reception you can either request a first generation meter that uses this network, but may experience difficulties sending readings to your supplier automatically. Alternatively, you can contact your energy supplier and insist that they install a second generation meter, known as SMETS2. A SMETS2 meter is not reliant upon the mobile phone network and by the end of the rollout this network will have coverage of 99.25% of Great Britain.