It was founded in 2022 by Olivia Raisner, Nathaniel Horwitz, and Sam Koppelman in response to the Dobbs v. Jackson.
A tranny (female to male), and men, one a journalist, the other a biotech.
Meet Olivia Raisner, Joe Biden's Out Gay Traveling Digital Director Out, 30 October 2020.Trying to pierce the lack of direct links, major donors seem rarely mentioned. I suspect USAID had a hand in funding, prior to the election of President Trump. Note the article above and the founding of Mayday coincide.
But additionally, Largest donors to Mayday ---
Hopewell Fund -- "The Hopewell Fund serves as the fiscal sponsor for various left-leaning political projects. The Hopewell Fund spent over $127 million in 2020, and is one of the five largest nonprofits associated with the Democratic Party.", Global Impact, David and Lucile Packard Foundation and 16 smaller funds.
As to the Mayday HQ, the address they note is: 5 Avenue A, New York City. That is a four story, 13-unit rental building in the East Village.