A few days ago you could only order the Mac mini with M1 Chip with the option "Gigabit Ethernet", now when you are configuring your new Mac at the point of sale there is an additional option: "10 Gigabit Ethernet" to choose from if you want a faster LAN.
The faster version of the M1 Mac mini will not be available until 6 May 2021.
The 10 Gigabit Ethernet option will cost £100/$100 more.
The RJ-45 port in the Mac mini can now be upgraded to the speeds of the Nbase-T standard with 1 Gbit, 2.5 Gbit, 5 Gbit and 10 Gbit. The Intel Mac mini offered the upgrade to 10 Gigabit Ethernet even before that.
Before buying check Apple's support document for the compatibility of your own cabling with Apple's computer. According to the manufacturer, not every generation of copper cable allows maximum transmission rates of 10 gigabits: A standard cable with twisted wire pairs of category 6 will only support the maximum speed with a cable length of 55 meters. Category 6a or newer of the twisted pair copper cable is required for a length of 100 meters.