How to make the computer think that the modem is not a cellular connection?

Question

Python

The question itself does not accurately describe the essence of this problem, so I will explain.
For starters, there is a USB Modem, to which, like everyone else, the modem program and driver itself are provided. With this, everything is clear. The point is different, namely:
1. The mobile hot spot does not see the mobile (cellular) network.
2. When connecting a local network (Well, connecting 2 PCs with a LAN wire), the Internet disappears (The modem program shows that there is Internet, but the download and upload speed is 0.).
I solved all these problems by accident and now I can not understand how. Actually, the question itself is related to this topic.
What I did:
I dug into the device manager and removed all devices (Including the drivers for these devices) from the system that relate to network connections. All the main attention rests on the modem itself. Removed the modem driver. That is, the Internet completely stopped working. After that, for some time I could not restore it (even completely deleted the modem program and reinstalled it from the disk) after 2 removal of all modem programs, I went to the device manager and there was the modem network device itself (but it was displayed as unidentified). I clicked on it "update driver" and selected the previously copied folder of the installed modem program as the source and, accordingly, the driver was found and installed. Everything is fine. The problems I presented earlier have been resolved.
What is most interesting is that in network connections, the modem connection was displayed as a normal network connection over a local network and the icon on the taskbar was also displayed as a network connection (that is, there were no antennas), the operating system (Win10) did not recognize this connection as "Cellular".
After installing the modem program itself, this effect disappeared and I could not repeat it.
Therefore, the question is how this effect turned out and how it can be repeated.

Answer 1

Let's start with the basics. A USB modem in the system can be defined in the system in 2 ways: as a telephone connection, with a modem, and as an RNDIS device - Ethernet connection emulation via USB.
In the first case, the establishment of the connection is entirely provided by the OS. In the case of RNDIS, the modem itself stores the provider's settings and connects and disconnects the connection; for the OS, it looks like a regular Ethernet router. In this version, the USB modem can establish a connection, even just plugged into a USB charger.
Switching modes of the modem depends on the model of the modem, using special AT commands. The rest is configured by OS routing and firewall rules.

Answer 2

When you connect a local network, your default route comes from DHCP, and, apparently, its metric is lower, so the connection through can no longer be used.

Answer 3

No need to suffer garbage and try to distribute the Internet from the modem to the local network using a laptop. Let the Internet distribute the router, or the modem itself at worst, if it's not a completely stupid USB appendage.
Then the modem (or a router with a modem) will distribute the Internet, and all computers and a laptop will be taken, and there will simply be no place where a problem may arise.