Enumeration of the entire DNS space is not available in general, but it does appear that some TLDs offer complete zone files for legitimate research purposes, s

Enumeration of the entire DNS space is not available in general, but it does appear that some TLDs offer complete zone files for legitimate research purposes, see for example https://czds.icann.org/help#zone-files https://czds.icann.org/help#zone-files