Welcome to Source Criticism 101.

You need to interrogate the claims being made by the sources, as well as their supporting evidence. For example, I know that when I do episodes with Invicta, I make sure to provide references to relevant texts for what I'm discussing.

Insofar as using them as your primary source for debates about history...that depends. If you do your research - even cursorily - and are fairly confident that the claims you're referencing are accurate, or at least make sense to you, then sure. If you just want to repeat what they're saying on the channel, then make sure that you say you're being unambiguous about the people you're quoting and that you're not 100% sure if they're accurate.

I wrote the primary scripts for the Belisarius episode scripts for Kings and Generals.

Between you and me, there was a miscommunication on the Battle of Dara episode. The preamble is waffly and isn't critical enough of the sources imo. The animation is not what I had intended to be shown and is not accurate really at all. I intend to rectify this soon and release a corrected version with multiple sources, real-life topography map of the battle and possibly an interview with a world expert; it's going to be very lit.

Ad Decimum is better and I'd say 97% true to the picture in my head. There are slight fudges with the animation such as Ammatas' marching column from Carthage and the routing of the Roman foederati from the top of the hill but they don't change the overall picture.

The Siege of Rome is good but too short. The script had to be edited to no end to fit everything in; you missed out the beautiful bit about camel circles:

"In 534AD, a number of Moorish tribes in Byzacena and Numidia began an uprising. Solomon led a Roman force to fight the Moors. At Mamma, the Romans and Moors engaged. The Moors had a very original strategy. They deployed next to the foothills of the mountains and formed a circle of camels, twelve camels wide, surrounding themselves and their women and children. Initially, this proved to be effective as the Roman cavalry were unwilling to approach the camels, due to their strange sight, smell and sounds. The Moors used this opportunity to harass the Romans by throwing javelins at them and retreating. Solomon, noting that the side of the circle closest to the mountains was the least defended, dismounted his men and began hacking his way in. Having killed 200 camels, the Romans broke into the centre and the Moors panicked, with the majority being captured. A further very decisive victory was achieved at Mt. Bourgaon in early 535AD. Operations would continue in Africa for the next fifteen years, whilst Justinian further stretched his forces into Italy." [1]

That last line was also a point of annoyance for me. The series is far too pro-Justinian. I'm not actually a fan of Justinian and I wrote the criticisms that Extra History left out into my scripts but they were pretty much edited out, which is a shame as Prokopios is very anti-Justinian.

It's also wrong at points... https://youtube/Wq3bJAyZqMI?t=7m50s

At 7:50, "The Romans deployed a force to the West" the video shows a force being deployed to the East. But the whole point is that that force was meant to be on the other side of the Tiber and could have flanked the Goths from the back across the Milvian Bridge. But oh well.

So these videos are good for getting someone interested and they serve that purpose, as demonstrated by me, your lay historian. Are they accurate? Not always, very variable mileage. If they show an accurate/real battle map, then they're more likely to be accurate as the topography constrains the innaccuracy of the animation... Finally, there is no room for uncertainty. Videos for entertainment are not really a good method for bringing up a discussion of how these events may or may not have unfolded and points where the sources themselves are quiet or, worse, in active disagreement.

[1]: "Siege of Rome script finished", My Documents, 2017

The only channel of those listed I know is Historia Civilis. I have a bachelor's degree in History and have written several papers on ancient Rome. I've also developed my own game based on the Roman Republican public offices (a topic HC has done a series on), and have done quite a bit of research on the topic.

I find Historia Civilis to be exeptionally good at making complex historical questions understandable for everyone. I don't know everything, but the topics in which I am quite knowledgeable (primarily Roman history, and partly the Cleopatra's Egypt video) I haven't found serious issues, even though some details have been condensed (which is quite understandable in a video).

Overall I give Historia Civilis a big thumps up and I wouldn't hesitate to use Historia Civilis to get a good overview, and for friendly discussions. As others have said though: if you want to go into deeper discutions (or papers) it is always better to read the sources yourself (even though that takes more efford and time ;) )

I can't comment on the individual videos/channels as some others are, but in general I think the most important thing to keep in mind, as with any source, is their limitations. Acknowledge that you've gotten your information from a YouTube video, so you can't be fully confident in its accuracy and your conclusions based on it. No source is infallible, and half the trick of doing history is knowing the limits of what you're using.

This also feeds into the forum you're making claims in - if it's a discussion with friends, ultimately the burden of proof is what you want it to be. I've marked students down in essays (heavily, sometimes) for using these kind of sources, because for university-level history it's vital you show that you've been able to evaluate claims critically rather than just repeated what you've read, and a lot of history media just doesnt give you the tools to do that. The problem is not that they're necessarily wrong, it's that you can't tell whether they are or not because they aren't required to show you their evidence (and, if they do, why not just use the evidence directly?). The point is not to trust academic sources unconditionally, but to use their scholarly apparatus to evaluate the basis of their claims on your own terms.