Using the theory of civil law to analyze, we can think that the landlord has the real right to his house, and you only have the right to use his house. When there is a conflict between the real right and the right to use, the real right shall prevail.
If the landlord cuts your wire, and the house is out of power and can't be used normally, it is a breach of contractual obligations, because electricity is the infrastructure for providing the house, and the landlord can't cut it privately. Network cable (the key is that you pull it from the outside, which affects the safety and beauty of the house) is not a necessary condition. The landlord can ask you to demolish his house for its safety and no hidden dangers.
Maybe you will feel something is wrong. The landlord's behavior is not improper in his management of the house. However, he is suspected of restricting competition. Do you want to see if there is any obvious gap between the network designated by the landlord and your external network? If there is, you can still negotiate with the landlord.