Heat Death is “a newsletter about yesterday, tomorrow, and all the crises in between.” They’re always looking to commission guest essays and pieces that fit with their “primary ethos – weird deep dives into history, ecology, culture, and the unexpected intersections between them.” They offer an honorarium of $50 to $75 per piece. The sweet spot for finished pieces is between 2,000 and 4,000 words, though they have commissioned longer pieces when the idea calls for it. For details, refer to this post and this page.