Some boxes in Ultra Compact format include an IR receiver so that you can use a remote - and if so you can probably train it to use your existing remote.
There are a lot of challenges with this whole activity but perhaps start with just FTA TV only - using a DVB USB dongle or other DVB receiver.
I imagine that streaming services and FTA TV catchup services would be quite uncooperative about giving you the necessary proprietary information.
To add a little angst and paranoia, here is how Android TV boxes and Smart TVs can be used for malevolent purposes:
…want to have a zombie TV in your living room?
As long as it doesn’t get up an walk around saying “… brains, brains, …” “Send more cops.”
I will be happy with even a Purism cap.
That is a tautology. Anything from Google today starts out with a malevolent purpose. That is its purpose. To be malevolent. A botnet is just the icing on the cake. 
I use a wireless 2.4 GHz USB remote as I find it more reliable than Bluetooth or IR. The remote itself has the option to program IR functions into it as well though. I think building in a dedicated receiver with the Steam Machine for example was a good move for a device meant to be connected to a TV to avoid the dongle