You can also use https://github.com/noperator/raink to brainstorm TLDs that are relevant to some topic you care about. For example:

    curl -s https://data.iana.org/TLD/tlds-alpha-by-domain.txt |
        raink -f /dev/stdin -p 'which of these TLDs is most related to the concept of "hacking"?' |
        jq -r 'map(.value)[:10]'
    
    [
      "BLACK",
      "COMSEC",
      "TOOLS",
      "SECURITY",
      "ZERO",
      "EXPOSED",
      "FORUM",
      "SHELL",
      "BOT",
      "SOFTWARE"
    ]

Those are all in the IANA list but not all can be registered—just showing as PoC. See https://bishopfox.com/blog/raink-llms-document-ranking for more background.