> “Why Thracians again?” Well, the simple answer is: Because of Lyudmila Zhivkova and the golden treasures

Bling and booze. No alphabet or culture strong enough to ward them against thorough hellenization, and that was even before the Romans conquered them. Is that really a good foundation to build an identity upon?
The treasures themselves were probably stolen.
Let’s not forget several Emperors had to transfer population from Asia Minor to re-hellenize Peloponessus and Thrace and you quickly get an idea about the odds of any remnants of Thracians as such existing north of the Haemus in the 6th century.