Besides Tridgell's venerable rsync, there exists a permissively licensed implementation[0] by openbsd.
When pulling data on MacOS from a Linux computer I would experiment hangs even when setting protocol versions to 29 or 28. What fixed for me was to just switch to the samba rsync program on MacOS.
https://news.ycombinator.com/item?id=43605846
Most openbsd people I know install the real version from ports.