I have not been able to rsync from master.bioconductor.org since 04/18/2021. Are the rsync services purposely disabled or are they not available for some other reason at this time? Validated lack of port 873/tcp access from home Internet connection also, so it is not a case of internal corporate firewalls getting in the way.
Yes rsync access has been restricted to ssh from known IP addresses; see https://bioconductor.org/about/mirrors/mirror-how-to and forward ssh key and IP address(es) to webmaster. Actually, the restriction has been temporarily reverted, so likely for the next week or so you will again have normal access.