Maybe it's just me, but an obscure post from an Italian forum is not really going to make me think that King Arthur actually was an Italian, and not as English nationalist propaganda told us before.
Reliable, you know what it means ?
About as much as you know what 'claim' means and 'one' of. You were not very specific in which claim you wanted me to get a reliable source for. I wasn't trying to prove King Arthur was actually inspired (stolen) from italy. I was just proving that I was not the first one to think about it and that I was also not the only one. In which that post is reliable for that.
I'm sorry did you want me to prove that King Authari was actually King Arthur?
The whole Alfar-Avar
Morganna-Organa
Arthur-Authari
Albion-Alboin
How about that Tiberius II was emperor just two years before Authari became King?
Lucius Tiberius - Tiberius
That really wasn't enough for you?
How about the interregnum often propagated in Arthurian legend? In which Arthur becomes king at the age of 15, often by being elected by the nobles of the land?
Authari became king also after an interregnum, in the 'prime of his youth' (teenager) and he was also elected.
How about the fact that the sword in the stone is KNOWN to be an Italian cop-out?
You won't find a 'reliable peer reviewed source' for this, but you CAN LITERALLY read it in the Historia Langobardorum and you can also read it in Geoffrey of Monmouth's book. You can cross check them for yourself which is much better than a 'peer reviewed source'. Doesn't take a rocket scientist mate, it does not take a rocket scientist, you can put two and two together on your own, you don't need someone to feed you from a bottle. In this world, there are many things we don't know, there are many things that we are not told, there are many things that we are lied to about the best judge isn't going to be some quack getting a paycheck from people who tell him what to write or what to say, it's not going to be me, it's going to be you. You're the one who will have to make the decision on what to believe based on what you find, there aren't always going to be a 'source' of someone with 'authority' to explain things to you, and hell sometimes they'll just flat out lie to your face. Saying that you won't believe something because there isn't a 'reliable source' is just a way for you to stay in your precious safety net.
I've given you the best sources you could possibly ask for (the two historical texts i've mentioned), I've given you the choice whether you want to investigate the matter or not, if not then shut the hell up about this and go back to living whatever glamorous life you were. But if you do read them then you can get back to me on the decision that you came to YOURSELF. Or is that just to much to ask?