Amazon's Fire TV is Adding Full-Screen Video Ads That Play When You Start Your Fire TV
(cordcuttersnews.com)
A lot of the fire tvs can be rooted! There’s a great community over at XDA with all the needed resources.
I have two 4k sticks (1st gen) rooted and debloated running Leanback launcher. When you cut out all the junk, it really is (or was?) the best 4k streaming device under $50.