Is the 10Gb port on the latest Mac Mini (2018) backwards compatible with 10/100/1000Base-T devices? I ask because the Apple site reports that the upgraded 10Gb port uses NBase-T.
Yes, it is compatible with both 1000Base-T and 100Base-T. I own the Mac Mini 2018 with 10 Gbps option and have tried both configurations in practice.
It doesn’t appear to be compatible with 10Base-T, but you’ll be hard pressed to find such equipment anywhere these days.
You can find Apple’s description of the network support at the following link:
It similarly describes that 100Base-T is a supported configuration, while 10Base-T is not. Look at the included table for instructions on which cable types to use for the various supported speeds.
Eventually, this should be compatible with 100/1000Base-T but not 10Base-T. Very little currently available hardware works with only 10Base-T. I suppose if you needed to interface with a 10Base-T device, you could just use a 10/100Base-T switch between the devices. These type of switches can be purchase for under 10 USD.
According to Apple's website: