Why does 'directly addressable' mean 'not behind a router'? Unless you've got a weird ISP that's delivering you Ethernet, you're going to need a router.
I have a gigabit fiber (to the home) connection which terminates at a device with 4 Ethernet jacks. They all work, I've tested connecting directly to them with a laptop, but I plug a router into it and all devices connect through that router instead. It's the 'stateful firewall' aspect of using a router that I want for improved security. https://en.wikipedia.org/wiki/Stateful_firewall
My ISP delivers me Ethernet... I doubt it's that uncommon in midrise/highrise buildings. But they will only route to a single IP address (incl for 64-bit) so then again I still need a router.
I have a gigabit fiber (to the home) connection which terminates at a device with 4 Ethernet jacks. They all work, I've tested connecting directly to them with a laptop, but I plug a router into it and all devices connect through that router instead. It's the 'stateful firewall' aspect of using a router that I want for improved security. https://en.wikipedia.org/wiki/Stateful_firewall