@quasaur The issue at hand here is the driver hasn't been written for Apple Silicon by Prolific yet.

There are a number of (not-free) apps in the Apple App Store that can supplant the driver need and allow you to do the direct-action in the OS to the device -- I've used a few of these over the years myself. And I haven't found a single USB->Serial device it cannot process yet.

You may find recommendations in the forum here from other users for Console applications for macOS that would fit the bill. I know of at least two that have 15- or 30-day free, no subscription trials that you can test run with to see if they fit your needs.

Hmm, that is odd. The switch chip in the 1100 connects to all the ports and is auto MDI/MDIX.

Do you see link with a straight through cable to the unmanaged external switch? It shouldn't make any difference.

Do you see a link with the laptop connected to the LAN or OPT ports? Those should also be identical.

Steve