The most important factor to consider is the source. And your source's source. What are their credentials? Are they just some people who like history talking about it? Do they make other content, and work some history in as 'popular' topics? Do they have any training in being a historian, or in public history? If the answer is "no, they don't have formal training", that certainly doesn't immediately exclude them. For example I commonly recommend Mike Duncan's podcasts, and while he later went back and got his Master's degree, when he first started The History of Rome he just had a Bachelor's in History. The one group I would stay away from? The "I make lots of different videos on interesting subjects, so here is a 6 min video telling you all about WWII". There is simply no way possible to distill down such a broad, complex topic into a 6 minute episode that you've only researched for a week to make a video.

Once you've evaluated your source, and keep in mind any biases they may be bringing to the table, you need to evaluate their source. This is crucial. So many times we take things as face value because it's.... there. This goes for books too. Just because someone wrote something in a book doesn't make it true; for example I recently purchased and then regretted purchasing a biography of Louis XVI by a former History Professor (good, reliable source, right?) but in it I found some wild claims. Upon checking his sources, I realized he was quoting verbatium from a diary of an incredibly biased source, without any critical evaluation. Despite his credentials, all trust was lost upon that first misuse of a historical source. Likewise in your YouTube videos, you should always be asking yourself, "Where did this person get this information?" You'd be shocked at how often, on YouTube, the answer to that question is "Wikipedia". I talk about it more here, which is another discussion on YouTube history videos, but when I dove into the channel OverSimplified's two-part series on the French Revolution I found that lots of 'facts' he used seemed to just come from the Wikipedia page, which often cited things like blogs for its sources. I consider these videos little more than fiction, and if people choose to watch them I would urge them not to think of what they're hearing as anything more than a crude rendering of an event.

Hopefully then, you'll find a video that cites sources, usually in the form of scholarly texts, whether that's journal articles or books. If the channel cites sources that are what are referred to as "tertiary" sources, i.e. Wikipedia, online encyclopedias, blogs, online articles (non-peer reviewed, as in an article by Medium), I would steer clear, or try to fact check the tertiary source, who should in turn have a citation. If they are relying fully on tertiary sources than I don't believe that's a channel with value to learning history. Tertiary sources are never going to be able to dive into complex topics, the viewpoints of different historical groups, and might be incredibly biased in, say, leaving out atrocities committed against certain peoples. Tertiary sources, especially online news articles, often do not quote sources at all, or maddeningly quote other news stories as their source. Websites like Wikipedia are fine as jumping off points to research something more deeply, but don't be fooled by the "sources" on a Wikipedia page. I've often found people using as "sources" personal blogs that they found which discuss the matter at hand, which is essentially the same as quoting someone's Instagram post as a source.

What if the channel or video doesn't have any citations? Well of course it's your call, but if they can't tell you where they're getting their information I wouldn't consider that a history channel. An extreme example might be a child who is only 8 or 9 coming across a "history" channel that teaches them that the Holocaust wasn't real, and gives "proof". This might be even before a child learns about the Holocaust in school or from their parents. If they're shown a video, without citations (or perhaps citing blogs or other propoganda) and then later taught about the Holocaust, they're going to be conflicted, and might reject what they're learning as false. Of course this is an extreme example, however this happens in smaller forms when we watch videos without sources on any other subject. I do not think it's worth it, even if you approach these videos as pure fiction.

"Yeah yeah yeah" you might be thinking, "but what about the channels I listed?" So I looked one up: The Armchair Historian. I clicked at random on a recent video, which can be found here, and is called, "Why was Italy so Ineffective in WWII?", which they apparently cover in 8 minutes. The first screen is an ad, and the first thing in the description is an ad. That tells me this channel is very monetized and motivated to put out a lot of videos, which isn't necessarily conducive to good, thoughtful history. Okay so what are their sources? Two YouTube videos (yikes) and a list of a few books, without reference to page numbers or even chapters. Of the two YouTube videos cited, one lists zero sources for their own video. So they're getting this information from some other random person who lists no sources. That tells me the armchair historian doesn't really care about telling accurate history. The other YouTube video cited lists almost the exact same books as they do, making me wonder if they just copied that person's book list. On that book list, alarmingly, amazingly, one of the books is written by a Nazi. No joke. Frank Joseph. A literal Nazi is their source material. I sure as hell hope they make that VERY clear in the video, because I'm not sure you could call a history book written by a Nazi unbiased. Even if he's just using that book for military purposes I hope he actually read it himself, and knows who the author is and what views they might perpetrate in their writings. Frankly off of that one video alone I wouldn't care to watch anything they put out, since they don't seem to really know what they're talking about without citing other people's YouTube videos. It's just not history, it's a work of fiction meant for entertainment purposes only. I would highly encourage you to check the sources on your other video channels and see if they hold up to scrutiny.

Unfortunately I have never encountered a YouTube channel that makes good, sound history content. I do think that there are some podcasts that are worthwhile. The only one I can speak to is Mike Duncan's History of Rome series and Revolutions series. I also think that at times we have a knee-jerk reaction to books as boring and dismiss them outright. I personally have found some historians who write on the French Revolution whom I love, and I find their works actually fun to read. I'd encourage you to give the booklist on AskHistorians a try if you're looking for good content. If you're still looking for videos, maybe consider searching the sub for videos on different subjects, as I'm sure they've been recommended before. I wish you the best of luck in finding good content, but unfortunately I don't think YouTube is a great spot to try and find it.