September 2021 update: The ads are now live! As a way to try to address some of the concerns about the voting period being too short, we're running the selected ads that score 6 or more, or any ads scoring 4 or more with no downvotes. You can see the full list of selected ads by running this query (thanks to Glorfindel and Slate for the help with it). From the 34 sites selected for the trial, 30 sites had at least one ad proposal, and 24 have at least one ad making it through the score threshold to be displayed; a total of 119 ads were selected, and Code Golf & Coding Challenges was the site with the most ads selected, with 19 selected proposals.
June 2021 update: The ad collection posts on all of the sites listed below for the trial period have been posted. Submissions and voting will be open through August 2nd. Thank you for all the feedback — I tried to address most of it, and hope to be able to address some of the outstanding concerns (particularly surrounding ad rotation, etc.) after the trial is over.