in which case unless you have 18awg copper lines around, you can't do 1km :)

I would be shocked if anyone has those. Maybe alarm wire I guess?

I've got a 3 pair run[1] to my gate with a keypad gate controller. Two pair are used for voice communications, and one pair is idle. The gate controller has 10 base T ethernet (for management), but you need two pair, and it's maybe a touch outside the distance spec for 10baseT. I'm not quite ready to spend $350 to get it on ethernet though.

[1] Actually, it's 4 pair to an in-ground junction box, where it splices to 3 pair to the gate controller. For $350, I have maybe some other other options around the junction box (I've already got some passive 10baseT <-> single pair devices, but they don't work at the full distance. Probably would work at the junction box, if I had a powered ethernet switch there, but I need weatherproofing.

Unlike the 1km, this doesn't require 18awg wire :)

10Base-T1L may replace RS-485 in forms of process automation, but the length capability is not the particularly interesting feature there :)