Best tools to use & references
DNS Lookup:
https://intodns.com/
https://www.ns-lookup.io/
https://dnscheck.pingdom.com
https://intodns.com/
https://www.ns-lookup.io/
https://dnscheck.pingdom.com
Domain Search:
https://lookup.icann.org/
https://uniregistry.com/
.FR domain search: https://www.afnic.fr/fr/produits-et-services/services/whois/