Would like to keep in mind the last of the Prussian nobility only died within many Redditor's lifetimes. This is still very recent history.

Read up on the Prussians in Český Těšín in Czechia. https://kamusella.wordpress.com/2017/05/23/last-prussians-or-translatio-borussiae/

In effect, the Prussians in northeast Czech Republic were so far out in the woods that no conquering polity ever fully replaced their Prussian language/society/identity, simply because it wasn't worth the time of the conqueror to deal with it. The local community has now rebuilt/restored some of their Prussian language and folk history and cultural identity.

Let me amend this: https://core.ac.uk/download/pdf/9548638.pdf?repositoryId=95

Likewise, there is no movement in the Czech Republic for reclaiming the defunct tradition of Łysohorsky’s Lachian language or creating a Czech Silesian language. The nascent grassroots support for the Prussian language in the Hlučínsko has not moved yet beyond using it for regional (folkloristic) poetry and collections of stories. In a way all the traditions remain unclaimed for a language-building project, and are thus ‘fair game’ for the builders of the Silesian language, as indicated by Roczniok’s repossession of Łysohorsky as a (national?) Silesian poet. The problem is that in the Czech Republic, Těšín Silesian and Prussian are written using Czech spelling, while the newly developed standard Silesian orthography follows Polish orthography, although diacritical letters not occurring either in Polish or Czech (for example, [ō] and [ô]) are employed. It may hinder the acceptance of standard Silesian and its spelling system among the Czech Republic’s Těšín Silesian- and Prussian-speakers.

Also, I learned of this because my surname is from the neighboring region, and has over 120 spelling variations due to the trilingual nature of ever changing borders over there during the centuries.

Edit:

u/Fierce_Lito has provided a wonderful article about the original Prussians (before various German groups migrated/conquered east to establish a German class of rulers, burgers, and merchants largely in urban areas). The article covers everything I discuss here, but is much longer. If you have the time, definitely read it!

Seeing as no modern historians have responded, I'll give my thoughts:

First, I cannot speak for people who self-identify as Prussian, and by doing so are recalling either the Kingdom of Prussia in the days of Otto von Bismarck and the Wilhelms, Friedrich II and his famous battles against Austrians, Russians, and the French; or Ducal Prussia from which Brandenburg ascended into kingship in the reign of Friedrich III. (or, as king, Friedrich I.) as “King in Prussia” -- thus creating the polity as we know it, even though the primary residence and court was in Berlin, the center of the Electorate of Brandenburg. If you mean identification in the sense of people groups, like we would say Bavarian, Saxon, etc., then no. There are no Germans groups who identify as Prussian.

Part of the problem is there was not, compared to Bavaria, Saxony, Franconia, etc., a strong Prussian national identity. Prussia’s numerous territories were tied to the Kingdom of Prussia through direct links to the ruler, instead of through a uniform sense of belonging to a greater political entity called Prussia. This tradition dated back to the 1600s, when Ducal Prussia’s only loyalty was to the duke, a Hohenzollern, not to “Brandenburg,” “Brandenburg-Prussia,” or some other greater political entity (the same was true for eastern Pomerania after the 30 Year’s War). Ducal Prussia had its own Privy Council (responsible for many aspects of governance in the ruler's absence), separate from Brandenburg’s.

Even still, there were Prussians, why don’t they identify as Prussian? Well, arguably the greatest killer of “Prussian identity” was the Nazi’s incorporation and glorification of the “Prussian military” into their own propaganda apparatus. “Prussia” was largely dead by the time the Nazis took over, and Christopher Clark states that the Nazi’s just never took the time to legally abolish the Prussian state. By incorporating their own idealized view of Prussian militarism into their self-image and mythos, the Nazi’s also guaranteed Prussia’s official destruction: as the Allies formally eradicated Prussia in 1947 through the Control Council Law No. 46 after claiming Prussia was the source of all of Germany’s ills. This law opens with:

The Prussian State which from early days has been a bearer of militarism and reaction in Germany has de facto ceased to exist.

Clark also provides evidence of expellees during the German ethnic cleansings of the middle of the 1940s. These expellees into other lands, from Prussia, did not identify themselves as Prussian. Instead, they referred to themselves based on prominent cities or states (Länder) as Pomeranian, Silesian, etc. Later, these expellees in France, the UK, or USA identified themselves simply as German during periods of political activism. Clark’s conclusion? Prussian identity had diminished long before its formal and legal destruction in 1947.

The Nazi element is also important to note, as Germans today who would call themselves Prussian do not evoke the image of someone knowledgeable of their history, but rather someone desiring the “Prussian” image and myth invented by the Nazis.

In conclusion: Prussian “identity” was already greatly diminished (if such any strong identity existed in the first place!) before the Nazis took over and distorted Prussian identity into their own. Those who still retained a genuine feeling of Prussian identity also generally left that identity behind after the Nazis corrupted their idealized version of Prussia, before the Third Reich was eradicated. Now, “Prussian identity” recalls militarism, jingoism, and warfare -- itself a shadow of the complexities and nuances encompassed in a historical polity of numerous cultures, languages, stories, and accounts over hundreds of years.

Source:

Christopher Clark. Iron Kingdom: The Rise and Downfall of Prussia, 1600-1947. Cambridge: Harvard University Press, 2006.