For a while, (up to including Sequioa 15.3) both rsync_samba and rsync_openrsync were available, via /var/select/rsync or the env variable CHOSEN_RSYNC.

One particular annoyance of openrsync is that it claimed to support the /./ magic path element for --relative. I sent a bug report to Apple for this about a month ago.

rsync_samba is gone as of Sequoia 15.4.

I've installed rsync from homebrew.