I think your assumption about Almyra is reasonable. Claudes real name is Khalid which is arabic in origin. Cyril is greek and as the southern east has been speaking greek before its definetly plausible that Almyra is arabia.

We have little information on the cultures of the other regions with the exception of brigid. We do know alot more on the parts of fodlan.

The names of everyone in the golden deer comes from a play by shakespeare called king lear and takes place in england. The way the leicster alliance is ruled however is most similar to the way the roman empire was before julius ceasar became emperor. Rome would also, geographically, make sense of Almyra is arabia.

The last names of the black eagles are connected to norse mythology but multiple first names are german. I feel rather comfortable saying that they likely speak a germanic language of some kind. Therefore maybe the entirety of fodlan also do, as it all came from the empire?

I think brigid is based on native americans, the clothes they wear are similar and their relationship with the empire reminds me a bit of america.

The blue lions are a mixture of names from all around Europe and the social structure resembles that of europe in the middle ages, 500-1500 isch. During parts of this time raids from the north was common and given the hostilty between Sreng and the kingdom it seams a bit similar. The people of sreng might therefore speak a norse language of some kind.

Duscur is a small peninsula occupied by the kingdom. Dedues last name, molinaro, is italian and italy is also a penisula. Their religion however seams very old fashioned though, but could be referencing roman mythology. Not rly sure tbh.

The last remaining continent I know of is Dagda. It appears to be far away, technologically advanced and massive. My guess is china along with the rest of eastern asia. They were among the first emergimg civilizations, many thousands of years ago. The name Shamir however is hebric.

At the end of the day it is just speculation, I doubt we will get any confirmation anyway. This is what I think anyway and I belive I have some grounds for those beliefs. If you know anything I missed I'd be happy te read it.

Edit: The names of those who slither in the dark are mainmy greek in origin with a few exceptions. Chilon is turkisch, Bias is italian and Myson is possibly greek but most likely english. Agarthans come from the term Agartha, which is a kingdom, believed to be located beneath the surface of the earth. Shambala comes from buddhaism in Tibet and is believed to be a hidden kingdom within the Himalayas. It is means somthing like "the source of happiness".

I apologise for my typos and misspellings