Everyone - just to be clear - I am a retired Chemist, not an EE. The company supplied their own router - it is a Calix GigaPoint GP1101X. I am hard wired via Ethernet from their router to both streamer/dacs (LUMIN T2 and LUMIN D2). I have two big stereo systems. I run all 3 4k Sony TVs wirelessly via my EERO system which is also hard wired via Ethernet to the new Router.
I hope this helps.
Thanks to sfgak for his much more detailed response