UPNP Capability

I have a WD MyCloud Home cloud drive that requires UPNP to be enabled, Unfortunately, the AT&T Gateway does not allow for UPNP. I have a Linksys WRT1900AC Router that does allow for UPNP. My questions are:

• Has anyone else ever set up this router with the BGW210 and if so, how?

• Also, I am assuming that once I get the WRT1900AC set up, I will be able to use my WD MyCloud by simply plugging it into the WRT1900AC rather than the BGW210.

• Why in the world would AT&T not have UPNP capability!?