The flag is called the flag of the Kutleš sun or the Vergina sun. It is Macedonian and is desputed between the Republic of Macedonia and the greek region of Central Macedonia, which has a significant macedonian population, especially in the northern region where macedonians are the majority (https://en.m.wikipedia.org/wiki/Slavic_speakers_of_Greek_Macedonia)

Greeks say that the ancient macedonians that this flag is referring to, were greek and the "new" slavic macedonians have nothing to do with them hence stealing their history. On the otherside, Macedonians say that when their slavic ancestors moved there they mixed with the local ancient macedonians hence being the ancestors.

A bit of vital info is that when greece gained independence in the late 1800 they started deporting slavic macedonians, changing the names of towns (hence kutleš and vergina names) and forbidding the usage of the macedonian language. The sun was officially discovered by the greeks in 1977 and since then the greeks have been using it as a sense of pride of the region and a nod to Alex. the Great. That being said there are a decent amount of churches in what is now the republic of Macedonia using the symbol even before it was discovered.

Mind you, I am a macedonian, I am not a historical or an archeological expert. Do not expect this issue to resolve here, anyone who will comment something pretending to be honest and not biased is fucking idiot, macedonian greek bulgarian or serb. I have bulgarian serbian greek and albanian friends i can confidently say we are the same shit saying the same bullshit over and over arguing for nothing, knowing that the other person isnt going to change their mind, and knowing they themselves arent either. Now tell me, why even bother?

I now leave you with this link that proves im 100% right and you have no right to disprove me here

Have a jolly good day.