Roku TVs "phone home" a lot. I had one with pihole blocking it's collection, but they still updated my menus to suggest garbage for me. I wasn't willing to let the device go un-patched and still be on my networks, so there was probably still data getting back to them. A computer is easier to secure but still has all the same issues by default. The difference is that a computer isn't designed to spy on you. Netflix in a browser is still going to tell Netflix about your viewing habits, but at least it doesn't tell Roku via screen scraping as well.
Same here. Nvidia shield with FDroid sideloaded and a custom launcher is pretty solid.
No Ads with the custom launcher.
I don't have to be logged into anything I don't want to be, the devices are... not excellent but probably the best you can get right now for the price range.
Media format compatibility is good. Bluetooth connectivity exists for peripherals (incl audio bars and headphones). It has USB ports to take a thumbdrive or other android support peripherals (incl USB audio DACs).
Good support for CEC and the remote has IR support for controlling other hardware (ex - I can make it work with my Epson projector just fine).
I don't really like the toblerone remote form factor - and it should be against the law into include dedicated streaming service buttons (netflix... blegh), plus every now and then I have to reboot the device. But generally speaking... if one died I'd probably buy another as the replacement.