We pick g.root-servers.net, one of the 13 root servers (1), and ask it about ns4.alternatifweb.com and learn that com is delegated to 13 name servers (2), so we ask f.gtld-servers.net where we learn that alternatifweb.com is delegated to two name servers, including ns4.alternatifweb.com (3), so we ask that one and get the following answer:
The primary name server ns3.alternatifweb.com only
All of the six domains that use the primary name server ns3.alternatifweb.com use name server group 1. Worth noting is that all of the domains that use name server group 1 use the primary name server ns3.alternatifweb.com.
The two name servers ns3 and ns4.alternatifweb.com together
There are six domains that use name server group 1.
All of those are under the tld "com".
All of them use the primary name server ns3.alternatifweb.com. Worth noting is that all of the domains that use the primary name server ns3.alternatifweb.com use name server group 1.
All of them point only to the IP number 80.83.119.21.