I use older Roku's for YTTV - as mentioned, Roku and YTTV are still at odds, but Roku's that had it installed when the spat occurred are grandfathered in.
Otherwise, I love YTTV. Yes, I only get the Chicago NBS Sports Net (White Sox) for an RSN, but it has most everything else for sports in the base package. I split my subscription with my brother, so I pay $35/month (base sub is $70) + $10 for the sports pack (next to worthless except for Red Zone) during NFL season. I haven't bit on their 4k subscription yet, don't watch enough TV to warrant it.
My living room TV has the app built in, but recently I've been having dropout issues with YTTV on it (it's a 2 year old Vizio Quantum 4k - the issue ONLY occurs with the TV's YTTV app, Roku's and PC's work fine) - so if you go the smart TV route choose carefully and do your research. I also use wired ethernet cat 6 instead of wifi to get the internet to the TV, which seems to help when streaming Youtube (not YTTV) 4k content.
You must have a pretty good internet setup to make streaming work with 4k...I have DSL w) 40 Mbps download and thankfully I don't have more than 1 TV going at most times. I have had 3 TV's going at 1080p at the same time and that worked fine.