For all non-Docker environments, you can find the files for manual download in our repository by selecting "Stable Preview" for your OS.
For Docker, you can pull the 12.0-rc3 or preview tags.
For the full changelog, please see the GitHub releases:
https://github.com/jellyfin/jellyfin/releases/tag/v12.0-rc3
https://github.com/jellyfin/jellyfin-web/releases/tag/v12.0-rc3