Is the Dunning-Krugger effect is mainly displayed by low education people?

In my own personal experience pretty much everybody displays that in areas outside their expertise, and I definitely include myself in this.

For example the phenomenon of people offering what basically amounts to Medical advice is incredibly common outside the Medical profession.

It’s also my experience that highly educated people don’t have any greater introspection abilities than the rest (i.e. for self-analysis and self-criticism) or empathy (to spot when other people feel that you’re talking of your ass).

Maybe it’s the environment I grew in, or the degrees I learned and professional occupations I had (so, Physics, Electronics Engineering, Software Engineering) that are too limited to make a judgement, maybe it’s me showing my own Dunning-Kruger effect or maybe my observations are actually representative and reasonably correct: whichever way, my 2c is that learned people are no better at the adult mature skills (such as introspection and empathy) than the rest, something which also matches with my experience that the Education System (at least were I studied, Portugal of the 80s and 90s) doesn’t at all teach those personal skills.

So IMHO, your assumption that the majority of those people have low education is probably incorrect, unless you’re anchoring that on the statistic that most human beings on Planet Earth have low education, in which case they’re certainly the majority of the confidently incorrect even if they’re no more likely to be so than the rest simply because there’s more of them than of the rest.

PS: Also note that amongst highly educated people there are people from different areas which emphasize different modes of thinking. My impression is that whilst STEM areas tend to emphasize analytical thinking, objectivity, assumption validation and precision, other areas actually require people to in many ways have a different relationship with objective reality (basically anything in which you’re supposed to persuade others).