The UK only requires you to have a TV licence if you watch BBC iPlayer, or watch any live TV / stream, even if that content is not produced by the BBC. Also, recording something live in order to watch it later requires a TV licence.
So, if you watch something live on Amazon Prime or YouTube, you need a TV licence. I don't know if the BBC define what 'live' actually means, there's always a delay.
I have a TV but don't have a TV licence. I don't own an aerial cable and it's been factory reset to detune all the channels (I used live in a house that had a TV licence). I use it with a Chromecast.
I have one of the 'threatening letters' next to me right now. They're all addressed to 'The Legal Occupier'. That's not my name. They can go **** themselves.
Live TV is awful.