My recommendation is a Sceptre. They make 65", 4K dumb panels. I bought mine last year and the picture is great, the UI is fast, because it's just a regular TV menu, and best of all it cost less than $400.
I have a Sceptre and a Vizio, and I bought another Sceptre fro my mother. For the price, the Sceptres are really great panels. However, a soundbar or a decent sound system is a must with them, their builtin audio sucks terribly. Also, they are a bit slow, and the remotes that come with them suck. Overall, I prefer my 10 year old Vizio, but for a good dumb display, the Sceptres are hard to beat for the price.
Since the transition to flat screens I haven't seen a tv with good audio. It could be my bias, but I think that you basically need external speakers with any tv right now.
Same, I would never rely on built in TV audio.
+1 for Sceptre. Mine is coming up on 7 years, and I've never had any maintenance issues w it.