Access your PC or NAS via the network where an apk is located ? Use an app like Total Commander.

Any usb that you can use to abd install from?

Wait what? Did DTVNow update their latest app or something? I haven't watched TV lately

Edit oh Snap you meant the boxes..dammit

On the directv now sub I remember reading folks sideloading Netflix but didn't work properly. What are you trying to sideload.

IMO you’re better off using a cheaper and more reliable underground IPTV service.