First of all, I would like to clarify that I'm asking at webapps.stackexchange.com community as suggested in this answer.
Well. This is a YouTube's live stream which was published by a content creator who recorded a multi-camera stream. So, if I'm not wrong, in theory we could switch to other people's webcam streams that were recorded too in that multi-camera stream.
I would like to know how can I see the other people's cameras/streams. Maybe can I add a parameter to the query of the YouTube video url?. If not, the how can I do it?. I don't see anything in the YouTube's user-interface to switch between recorded cameras during that live stream.
By the way, that is a "big" Spanish youtuber and in the comments section of that video there are thousands and thousands of people that are still writing comments (even right now, after the stream was finished many hours ago) with something that seems commands, like: "/cam2" – as a single, full commentary (and obviously those commands will not have any effect because they are literally publishing comments with that). And the same happened during the live chat in the live stream, thousand of people writing things like "/cam5" in the chat box, but when I wrote the command "/cam2" nothing happened. I don't understand if those users were just trolls, or they were trying random things to discover how to switch between cameras… asking himself the same question as I'm asking here in StackExchange.
Best Answer
The stream you linked doesn't appear to be a proper "multi-camera"* stream. For a proper multi camera stream, eg the SpaceX launches, there is a switch camera icon to the right of the quality gear.
Clicking the icon lets you choose freely between camera angles without affecting anyone else.
That creator you linked may have a chat bot listening that's executing commands on his streaming software to effectively provide multiple camera angles, but that's not the YouTube feature, that's something else. If it didn't do anything for you, chances are that it was just a "Monkey see, monkey do" situation that you can find in chats somewhat frequently (for example, typing
!dropto get in-game stuff is quite common on the Faceit streams, too, despite YouTube having implemented an actual button you can just click on).* Technically, multicam streams are completely different streams that happen to be available on the same URL. There's nothing stopping you from streaming a live feed from the arctic night together in a multicam stream together with some lions in africa and a live performance of Battleship Potemkin. The stream you were watching meanwhile is just a single stream that choses to broadcast certain images based on viewer input.