Overclocking the Odroid-N2 or N2+ requires your system to be updated with all packages to date (2021-02-23 in the case of Ubuntu Mate at the time of writing)
Code:
sudo apt update --fix-missing
sudo apt dist-upgrade
sudo reboot
Reboot is required after the upgrade!
Now you can edit /media/boot/config.ini and select the desired frequency:
N2
Supported Frequencies for Big Cores (Cortex-A73): 500, 667, 1000, 1200, 1398, 1512, 1608, 1704, 1800 (Stock), 1908, 2004
Supported Frequencies for Small Cores (Cortex-A53): 100, 250, 500, 667, 1000, 1200, 1398, 1512, 1608, 1704, 1896 (Stock), 1992
N2+
Supported Frequencies for Big Cores (Cortex-A73): 500, 667, 1000, 1200, 1398, 1512, 1608, 1704, 1800, 1908, 2016, 2100, 2208 (Stock), 2304, 2400
Supported Frequencies for Small Cores (Cortex-A53): 500, 667, 1000, 1200, 1398, 1512, 1608, 1704, 1800, 1908 (Stock), 2016
Note: Any frequency marked in RED is an overclock and stability may be at an issue. The N2+ needs the optional 80mm fan for these values! Once the fan is placed and set to run always the CPU temperatures remain below 40 degrees at my home (ambient temperatures between 15 degrees centigrade (winter) and 35 degrees centigrade (summer).
If you try a frequency that isn't supported it will default to stock!
While a fully overclocked (2147 MHz) Raspberry Pi4 will draw 11 Watt (or more), the overclocked Odroid-N2+ only draws about 6.2 Watt, according to Hardkernel.