It can range from explicit efforts to actively reach out to candidates from schools with students predominantly from historically-disadvantaged groups, to outright "no hiring of white men this quarter" (which is one of the more egregious documented cases, https://www.theverge.com/2018/3/2/17070624/google-youtube-wi...).

What I think most conservatives think it is: When choosing between a more qualified white cis man and a less qualified "diverse" candidate, some companies will pick the latter specifically due to DEI policies. I am very sure this is actually happening (see also e.g. the above source).

Turns out people don't like being explicitly discriminated against, even if they're from a majority group.