> The law says you need to be covered by a TV Licence to:
watch or record programmes as they’re being shown on TV, on any channel
watch or stream programmes live on an online TV service (such as ITV Hub, All 4, YouTube, Amazon Prime Video, Now TV, Sky Go, etc.)
download or watch any BBC programmes on BBC iPlayer.
> You are supposed to but a TV license if you watch YouTube or Amazon Prime Video???
This is not about those platforms in general; it is about the likes of BBC iPlayer app on those platforms. Only the latter require a TV licence.
It is my understanding that, for example, watching BBC programmes on BritBox (a subscription-based streaming service from BBC and ITV) does not require a TV licence. [1]