I think the bigger Altice set top box included a modem. I moved to a different apartment building in July 2021 and the installer replaced that box with a mini. I assumed that the standalone "gateway" box was a combination modem/router. But it appears to be only a router because gateway and router are separate items on the bill.
So where is the Gateway 6 I've been paying $10 per month? I checked the small trap door in one my hall closet and it contains a mess of unconnected coaxial cables and exposed circuitry.
I called Optimum and it turns out that both functions are in one box despite the two items on the bill:
gateway $10
router $0
Supposedly I can buy a modem and have the gateway charge removed. Argh.