Binaries for Bitcoin Core version v30.0rc3 are available from:

https://bitcoincore.org/bin/bitcoin-core-30.0/test.rc3/

Source code can be found under the signed tag

https://github.com/bitcoin/bitcoin/releases/tag/v30.0rc3

This is a release candidate for a new major version release.

Release notes for the release can be found here: https://github.com/bitcoin/bitcoin/pull/33559

There is also a testing guide here: https://github.com/bitcoin-core/bitcoin-devwiki/wiki/30.0-Release-Candidate-Testing-Guide

Release candidates are test versions for releases. When no critical problems are found, this release candidate will be tagged as v30.0.