The right way of making sure this doesn't become a monopoly is to treat this satellite infrastructure just as you treat the fiber infrastructure in many countries. Where instead of having the ISP owning the infrastructure, they can rent the usage of it, so you can have many competing companies using it.

So Starlink would be the infrastructure and they need to allow others to use it on the same level as the Starlink ISP uses it.

One example of this already working is in Sweden, where Telia-Sonera is owning the actual infrastructure but they have to allow others to use it as well. So in Sweden you have plenty of ISP choice, one of them being Telia-Sonera, but not only them.