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

Check out the "Root Zone Database",

https://www.iana.org/domains/root/db

(this doesn't have .yu)

This https://www.whoisxmlapi.com/whois-database-download.php is a start, but there's new ones every second so you're going to need to update a lot.

> apparently, "asking DNS servers for all the domains they know about" is not something you can really do anymore for security reasons. Guess that idea won't fly lol

There are actually a few nameservers that will just give all their domains to anyone who asks [0], but they are very much in the minority.

[0]: https://github.com/acidvegas/mdaxfr#tlds-that-allow-axfr

You could probably extract a lot from https://commoncrawl.org/