Not sure the answer to the monopoly thing,

• make it a publicly owned and operated municipal utility
• make the “last mile” publicly owned infrastructure and private service providers can connect to the data center that connects the last mile
• require that the company who owns and maintains the last mile can not also be a service provider over that last mile infrastructure

The last one is how Texas handles the power grid, so it would need a real regulatory body making sure the private last mile infrastructure is actually maintained, unlike the Texas power grid.