Something I missed: Mac OS sequoia is shipping with openrsync, the #OpenBSD version of rsync, created by Kristaps Dzonsons.
https://derflounder.wordpress.com/2025/04/06/rsync-replaced-with-openrsync-on-macos-sequoia/
Of course this is due to Apple not liking GPL V3, which is used by the latest version of rsync...
https://github.com/kristapsdz/openrsync
https://man.openbsd.org/openrsync


