You don't view "TV" over the Internet, usually. Yes, there are streaming providers that offer TV stations, but I think you get what I mean. You get TV stations over the air with an antenna, or via a cable or satellite connection.
But I believe the question is: can you use a Roku player on a Roku TV? The answer is yes you can. You have to remember which remote is which, as you'll need the TV remote to watch OTA TV and use the Ultra remote to control the Ultra. But yes, I've used a Roku player on a Roku TV without issue in the past. And you are correct that if the TV doesn't have an Ethernet jack the Ultra is the only player that has one. Most of the larger TVs do have Ethernet, but it's a brand option. Remember that Roku doesn't manufacture the TVs, they only provide the operating system. It's up to the TV builder to decide what hardware to offer.
Dan
Roku Stick (3600), Ultra (4640), Ultra (4670), Ultra (4800), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.