I think podcast sponsorships are also a pretty useful area to market/reach out to these "untapped" developers! A lot of folks I talk to don't consume active content in written/video form, but are much more likely to passively listen to a podcast and absorb some information that way.
Popular podcasts that I know reach out to tech and entrepeneurial folks: SyntaxFM, ReCode, Changelog, How I Built This, Masters of Scale, Software Engineering Unlocked, Programming Throwdown, etc. etc.