The workaround I've found is to send that segment a journey that populates tasks for its members (instead of a typical journey that, say, sends emails). See here for basic methodology: https://sirajabousaid.substack.com/p/easily-export-marketing-segment-members. However, I've found unworkable/impractical the final step there to export directly from tasks in Activities view. Instead, I make a contacts view with filters like the following:

Tasks (Regarding) Contains data

Subject Equals [NAME OF TASK]

I'm also interested in the converse of this problem, making a real-time segment from a contacts view (assuming that the fields selection in defining real-time segments can't do the job for whatever reason). If anyone has any solutions there, I'd be grateful.