This current Russian propaganda reminds me a lot of Nazi propaganda from 1939 that Western Poland was allegedly predominantly German-inhabited. That was of course not confirmed by Polish official censuses (in 1921 and 1931) and it was also not confirmed by data coming from the community of Polish Germans itself. The German minority in Poland carried out self-censues (they counted themselves) and the results were similar as in official Polish census - Germans were about 10% of inhabitants in Western Poland, not a huge minority or a majority as Hitler claimed.
For example in Pomeranian Voivodeship (the so called disputed "Polish Corridor" to the Baltic Sea):
1926 German self-census - ethnic Germans were 12.5% of inhabitants (117.251 people)
1934 German self-census - ethnic Germans were 9.9% of inhabitants
1931 Polish official census - ethnic Germans were 10.1% of inhabitants (109.696 people)
And some less official Polish estimates for Pomeranian Voivodeship:
1920 Kazimierz Kierski estimate - 11.3% Germans (109.196 people)
1927 Zygmunt Stolinski estimate - 9.37% Germans (95.460 people)
1938 "Statystyka Polska" - 9.7% Germans (105.400 people)
As you can see German self-census numbers and Polish census numbers & estimates are similar.
Here is a detailed ethnic map of the "Polish Corridor" in the 1930s -
https://i.imgur.com/FmY0QP8.jpg
While this is how Nazi maps showed the "Polish Corridor" in the 1930s -
https://www.bpb.de/cache/images/0/29...x666.jpg?50DB4
And here a Non-Nazi map, based on real data - this map was used to draw the borders at Versailles in 1919 -
https://i.imgur.com/vnNaPVH.png
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And in Poznan Voivodeship (also part of Western Poland, to the south of Pomeranian):
1931 Polish official census - 193.080 ethnic Germans (ca. 10% of the total population)
1934 German self-census - 208.986 ethnic Germans
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So as you can see Germans were about 10% in Western Poland - both according to Polish counts and their own self-counts.
But if you look at Nazi-made maps of ethnic distribution in Europe, they "painted" this area as at least 1/2 German-inhabited.
And Nazi maps also showed huge areas as German "Kulturboden" (inhabited by clear Polish majority, but culturally German).