There's lots of devices returned on a search for "android TV" on Amazon, but I'm looking for one that I can do the equivalent of rooting my phone and installing TWRP & Cyanogen (or any other custom ROM). Are there any TV devices that fit the bill for hackability like this?
adt-1.
keep in mind that true [a]tv-rom builds are relatively few.
I'm told that cm walked back from doing very much with their tv-builds. (are they now just producing tablet-UI builds for NP? or nothing?)
we'll see how open the xiaomi box is soon enough... fingers crossed
also, it sounds like you might be talking about generic android set top boxes, and not 'A'ndroid 'T''V' which is actual leanback... this reddit is for leanback devices.
If you're looking for hackable, you can't go wrong with a Nexus device, so I'd say go for the Nexus Player (or whatever replacement comes along for it).
The Nvidia Shield TV is also pretty open, and has a decent developer community.
You can unlock the Shield TV and install developer roms which come pre-rooted.
I would probably have just gone to xda to see which community is the most active.
"hacking"
Been looking into this myself as well lately.
For shield android TV, I came across this forum. The developer of an app called DROIDMOTE I believe is the maintainer.
http://www.videomap.it/forum/viewforum.php?f=25&sid=180d7b7fba3285850339a1853dd5e932
can do the equivalent of rooting my phone and installing TWRP & Cyanogen (or any other custom ROM)
....and then?
I think we can all agree that nearly everyone's end-goal on this specific subreddit is: "Watch things on my TV that I want to watch."
If what's in bold there above matches what your end goal is too... then doing things like rooting, ROM'ing, et al. might be unnecessary.
If your end-goal is: "Watch things on my TV that I want to watch... for free. " Even then, rooting & ROM'ing is not necessary.
So if what you're really looking for is that second thing I mentioned there, just let us know. There might be more elegant, better solutions you're not aware of. (Not trying to be a dick, just trying to help.)
Nexus Player
http://forum.xda-developers.com/nexus-player