A lot of conferences seem to have a sort of selective outreach component to their call for papers.

Conference organizers will go and post the CFP in various forums from which they'd like to get papers -- particular programming language forums, particular theory or practice forums, particular universities, etc. Some of this seems creative, like "we'd like to get more foo-lang people involved with bar-con this year." All that sounds like selective outreach.

If the conference values, say, diversity of background brought to the table, then those conference organizers could seek out and post the CFP in places that diversity might be found.

One of the difficulties is that it's hard to know what all diversity you're missing out on (much of it isn't visible, and much of it doesn't have familiar labels), but other of the diversity omissions are glaringly obvious.

Including the glaringly obvious omissions in one's outreach seems a good start.