(Sending this here because we've been discussing it on Slack but I want to make sure nobody missed out.)
In prep for an impending/very-very-soon release, I've drafted up a release list of PRs that I *think* went into yt-4.0. I generated this by running the gh command line and getting *everything* that targeted "main" (which was after yt-3.6 was released), everything that targeted "master" after April 13, 2020 (which was when yt 3.6 was released; this may include some 3.6.1 stuff) and everything that targeted yt-4.0 as a branch.
I think this may have let some other PRs slip, because we used other repositories for a while, but it should be reasonably complete.
This is not the "changelog" but it is the list of PRs.
Feel free to engage here on the list or on the gist with any suggested changes.
I'm working on now on the narrative changelog with high-level changes listed, which I'm basing on: