What to run
Use DNS Lookup, then Whois Lookup. DNS Lookup is DNS-over-HTTPS from the browser and does not follow CNAMEs. Whois is RDAP: registrar, statuses, dates, and nameservers.
How to read the result
NS answers are the servers publishing the zone.
RDAP nameservers are what the registry has.
If they differ, the registry has not caught up, or you are looking at a subdomain's own NS.
What to open next
Query NS, then compare to Whois.
TTL on the old NS explains delay.