Same problem.
rsync: [Receiver] failed to connect to feed.community.greenbone.net (45.135.106.142): Connection refused (111)
I get the same response from netcat as @Horfire:
root@kali:~# nc -vvv feed.community.greenbone.net 873
DNS fwd/rev mismatch: feed.community.greenbone.net != dl2.greenbone.net
feed.community.greenbone.net [45.135.106.142] 873 (rsync) : Connection refused
sent 0, rcvd 0
I also attempted to use a VPN and got the same result regardless of the country I picked.
Tried the connection via both IPv4 and IPv6, from digital ocean (Toronto - Canada) and my home network.