Hmm, maybe. Depends on the infrastructure they put up. If there is a separate domain for the telemetry, then you can block it. Still no guarantee that it still works though.
The app will need internet access to login though. That really is a cat and mouse game that is not worth your time I’d say.
Alright, that makes it a bit easier. Any luck so far in debugging the problem?
I would start with the minimal setup. Connect one of the non working machines to just the the switch, just to rule out any other equipment. Test all ports with this PC. repeat with the other two. Where are the similarities? Is something different?
Also, the TL-SG105E is a managed switch. Connect it to the working PC and open the web interface. Default IP of the switch is 192.168.0.1 if there is no DHCP lease. Make sure the IP is not used twice in your setup. Make a fimrware update, make a factory reset on the switch.
Well, time to post that Tom scott video again I guess.
https://www.youtube.com/watch?v=-5wpm-gesOY&t=6