@lain AA did a 3 hour panel on this question with Sargon + Apostolic Majesty (pro-roman) vs AA + someone else (anti-roman). I lean towards them not being Roman but they made a pretty good case to the contrary so I won't claim that lightly.
@Komnene@lain here's the stream I was talking about if you want to waste 3 hours of your life on the minutia of whether they were Roman or not https://youtu.be/jGppv--Bv-8
@Komnene@lain nah they're all arrogant youtubers with no credentials on the topic. although Apostolic Majesty is an actual gigabrain worth listening to
@lain@augustus Not to open the can of worms, but in case you're still interested
The byzantine time period is made to differentiate the organisation of religion and the common language. Greek was always popular with the upper classes, with Hellenization only the language spoken by the commoners changed and hence the laws and some titles were written in Greek
One of important differences between the orthodox and catholic churches is the power structure. The catholic church had the concept of Papoceasarism which placed the pope above the king and other patriarchs and equal to the emperor, while the orthodox were under the kings and emperors
The first doubts of them being Romans comes from the forged letters and decrees such as the Donatio Constantini, first started by Pippin and continued by Charlemagne that gave land and legitimacy to the papacy, the goal was to make the pope return the favor by granting the title emperor to Charlemagne, making him an equal in the western power structure
Another thing is education - the eastern court was educated in classical philosophy and kept the largest library of it while in letters to the pope, the Frankish kings would ask "what's the point of learning to read"
The nomadic Bulgars were also influenced, started using Greek in court and later used byzantine architects to build their capital in a roman style and claimed they were also successors to the roman empire. Later on, Russia also claimed that
The byzantine social organisation was also different from the rest of Europe, feudalism never really spread there as the legal and philosophical tradition wasn't broken. The commoners weren't tied to their land and had the freedom of movement, trade and could work different professions independent of guilds or lords
The distribution of power wasn't based on vassalage but on themes, which were either military or civic or both and there was regulation between them
They also had public chariot games like in antiquity which were influential in politics
On the question of identity, you were roman if you spoke Greek and accepted the laws and power of the monarch, ethnicity didn't matter, you could be Latin, Greek, Syrian, Armenian, Alan, Bulgar or from Scandinavia
So, I think it would be inaccurate to call them non-Romans, as they followed the lifestyle, way of thinking and had the social structure of Latin speaking Romans, that is also the opinion of my relevant professors on the subject. Maybe the most accurate term would be Rhomaion/Rhomaioi