Everything is in the title.
For instance in Switzerland, the Romansh are considered an ethnic minority, even though only 36'000 people speaks the language (or I should say the languages since it is almost a different language in each valley it seems).
However, since the 1990s Yugoslav wars massive waves of refugees came to the country and kept their language and culture, despite a good portion of them now wearing Swiss passports. In 2000 there was approximately 103'000 Serbo-Croatian people, 95'000 Albanians, 90'000 Portuguese, etc., but all of those numbers probably doubled since. There is today as much Kurdish speakers than Romansh speakers in Switzerland (that is, 35 thousand people), which is interesting since those are both endangered languages/cultures.
All of them are much more numerous than the Romanshs, but they are not considered to form an ethnic or national minority at all.
If the reason for so is that they arrived in the country recently, at which point will be they considered to have been here for long enough so that they become a national minority ?