Best linear power supply for Nucleus now?

Thomas, yes I can confirm that 5.5mm/2.5mm is the correct size. Danny @Roon also stated that himself in this post:

Regarding line voltage, there is no switch. They configure the power supply appropriately based on the voltage in use in your country. This is what Teddy Pardo says:

“Our products can be set to work as 110-120V or 220-240V. If you don’t specify anything, the voltage will be set according to the voltage in your country. If you require different voltage please specify it in your order.”