Ok. Most of my experience the switches will have 2 modes for each port: 1G/2.5G/10G/25G/100G or 10M/100M/1G/2.5G. This is typical for datacenter switches. Found this out when my trusty 10/100M USB dongle couldn't establish link. I needed to upgrade to a 1G USB3 dongle.

Now I want a datacenter switch with a gearshift for speeds, "high", "low" and "turbo" perhaps.

Half duplex is in spec at 100 as well as 10, so I'd be surprised if it didn't.