I am using a 7800 as an ADSL router (PPPoA) and have recently installed a Linksys WHW0302 Velop mesh system to upgrade my existing WiFi solution. The problem is that the Velop defaults to acting as a router and results in double NAT after completing the initial setup.
As I would like all my devices to operate on one LAN network so they can all see each other correctly, my options seems to be narrowed down to either setting the Velop into bridge mode (and losing most of it's management features e.g. Apple HomeKit Accessory Security) or setting my 7800 into some kind of bridge mode that would allow me to connect the Velop using ethernet in order to act as the router using my ISP PPPoA config.
Does anyone know if it is possible to use the 7800 in a bridge mode for PPPoA (I have read a number of cases using PPPoE, but not sure about how I would go about it if it currently connects over PPPoA)?
Furthermore, if I can use such a setup - are the unused ethernet ports on the 7800 able to be used for connecting to the Velop LAN? Like a switch? Logic is telling me this is not possible and I would need to connect a sperate ethernet switch to the Velop to give me more ethernet ports on that network.
I would be grateful for any advice you can give before I get stuck into testing this myself, as I'm trying something I've not done before here.

Cheers