AdbTether
Tether a Windows PC over ADB with no root and no app on the phone
...If the link drops, the PC stays offline instead of falling back to the local network, so traffic cannot leak out. IPv6 is blocked and address lookups stay inside the tunnel. Disconnect removes the routes and DNS settings it added; close the app and the PC is back on its normal network.
Free and open source (MIT). Needs Windows 10 1809+ / 11 (64-bit) and an Android phone with USB or Wi-Fi debugging.