Yes and no. People have figured out how to unlock the boot loader of some Fire TV devices, but it can sometimes involve opening up the device and making physica

Yes and no. People have figured out how to unlock the boot loader of some Fire TV devices, but it can sometimes involve opening up the device and making physical modifications (like shorting something on the motherboard) or having an older version of the Fire TV OS installed (it depends on the device). So yes, you can put an alternative ROM on some of these things, but I think the practicality of it isn't really there. I would just say "no", but someone will link to an XDA post showing how you can (at least on some Fire TV devices) through a really complicated setup that even a lot of people on HN wouldn't get though. If you actually want a custom rom, it's better to get something like an Nvidia Shield where you can just unlock the boot loader. The problem with the Nvidia Shield is that it isn't cheap like the Fire TV devices. It's priced more expensive than an Apple TV with less capable hardware ($130 gets you an Apple TV 4K with A15 processor getting 2,100 single-core and 5,100 multi-core, 4GB of RAM, and 64GB of storage; $150 gets you a Tegra X1+ with 300 single-core, 800 multi-core, 2GB of RAM, and 8GB storage). When a company's business model (like the Fire TV) is selling you cheap hardware and then pumping you full of ads, they often don't make it easy to avoid that.