What I was trying to say is that you shouldn't need their special modem. They gave me that same modem, and it's sitting on a shelf un-plugged in. I'm only using my own equipment.
I have quantum fiber at home, and I don't use their provided modem. The fiber terminates outside my house, and a cat5 cable was run into my utility closet, which plugs into the modem.
I have a Unifi USG router, and have the WAN configured for PPPoE login (you will have to get that login from the provided modem, or ask their support people).
You also have to set the VLAN ID to: 201
So as long as you can set VLAN ID on your WAN, and do PPPoE, you shouldn't need their provided modem.
With apologies for my previously cursed meme.