For areas with poor phone and RF signal, I would look for a mower that is camera-guided only, such as the TerraMow V1000. It navigates using vision rather than relying on satellite or cellular signals. You can see my review of it in action here: https://easylawnmowing.co.uk/terramow-v1000-review/

Alternatively, a LiDAR-guided lawnmower would work equally well as it doesn’t rely on Wi-Fi or 4G for its navigation. The YUKA Mini 2 is a great option for this; you can see it in action here: https://easylawnmowing.co.uk/mammotion-yuka-mini-2-review/

Kind regards, Mark