You seem to have bought the Vatican nonsense of the Serb & Croat migration from Belarus or wherever.
Serbs are native to the Balkans. Poles, Czechs, Russians, etc… all independently state they came from Serbia.
There is literally ZERO evidence for the 7th century Slav migration theory. Absolutely none. It’s based on a single Vatican forgery from the 16th-17th century, credited to Emperor Constantine VII Porphyrogenitus, which states something like “…and then I allowed the Slavs to settle there.”
Not only is there no evidence for it, but it is both logistically and logically impossible.
The genetic, archeological, written, anthropological, behavioural and cultural evidence for Serbs being indigenous to Europe is overwhelming.
Why did the Vatican decide to erase the Serb name from external records? As revenge for Despot Branković not recognising the Pope in the 15th century, and thusly having other Orthodox kingdoms pull their recognition as well, having already sent their respective recognitions.
The Albanians are from modern day Azerbaijan. They were brought over to Serbia by the Byzantine General George Maniakis via Arabia and then Sicily in the 11th century, and were allowed to stay to raise livestock for the Serb royalty.
Dalimil’s Chronicles are correct if you study actual history, not the German-Vatican propaganda that you find in schools.