If it's not an extension of nationalism, then why do you describe it as "ethno-nationalism?
Because ethno-nationalism is it's own ideology. The only similarity between civic (and pretty well all other forms of) nationalism and ethno-nationalism is the word 'nationalism'.
Ethno-nationalists completely redefine the term 'nation' to shoehorn in a nationalist identity, but under any meaningfully agreed upon definition of 'nation' ethno-nationalism cannot exist.
Nationalists of all stripes will vehemently disagree with ethno-nationalists on all fronts, because the ideologies do not even begin from the same base assumptions. The ethno-nationalists pervert the definition of the 'nation' to suit their needs; that's why I described it as a perversion of nationalism.
That's why I'm trying to get you to further clarify your message, because so far it has been unclear. You use the ambiguous term 'right-wingers' when you mean to speak solely of white supremacists, and then seem to imply that nationalism in itself leads to white supremacy, which is what I was disagreeing with. Your language thus far has not been specific enough, and it is leaving far too much ambiguity for your posts to be meaningfully understood.
Also, I would describe civic nationalism as a conservative philosophy rather than right wing.
That's not a useful distinction as the term 'right-wing' is most often defined as "the conservative or reactionary section of a political party or system." In the context of political discussion, 'right-wing' and 'conservative' are synonymous.
Further, the term 'right-wing' is not
that applicable to Trump anyway. His politics are built on populism, not right or left ideology. His social politics can rightly be defined as 'reactionary right-wing', but his economic views are an odd amalgamation of left-wing protectionism and right-wing laissez-faire domestic policy meant to appeal to his populist base.
Historically, populism doesn't fit that well in our modern left/right dynamic.