By way of update: FlakeHub has a record of all the NixOS 23.05 releases, and roughly 9 months of nixos-unstable releases. That means you can use our new CLI to help bisect. There’s details in our my post, `fh`, the CLI for FlakeHub, but for a quick taste:
$ fh list releases nixos/nixpkgs | grep 2305 | cut -d- -f2
453bb832f715dd6e51004c72dbd59b1556d554e1
c7ff1b9b95620ce8728c0d7bd501c458e6da9e04
aaef163eac75c2ac7f882c1fae4e0c08aa18d186
572d26930456132e7f2035340e3d88b36a5e9b6e
They’re ordered by semver, so the oldest releases are at the top, and the newest releases are at the end.