Available at: https://archives.boost.io/beta/1.86.0.beta1/source/ The SHA256 checksums are as follows: c62c9ab3c448ef4ed1b45f69631e3d7cc425fca96b991e5007b3af49f84344e1 boost_1_86_0_b1_rc2.zip 7e5b42428ed30a7ac9d832e9df9f5150a29d9cffe5aebde4d4c109da89f54b77 boost_1_86_0_b1_rc2.tar.gz 8718b092b37f04a739b647d154901d923fb3c3cdcff9f793d6a472e3f8e7c647 boost_1_86_0_b1_rc2.7z cd63cd3110fafbed8c196a82dd0f72c8600bc5c7fc218ede213947da3b721c06 boost_1_86_0_b1_rc2.tar.bz2 Changed libraries between RC1 and RC2: Boost.Process Boost.Odeint As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy. -- The Release Managers