[Tiberium]

You won't be able to scan most of websites this way because most servers expect you to also pass a valid hostname. However you can use domain lists, for example https://purecrawl.com/en/download/domains (or https://domains-monitor.com/ which is paid but has more domains) as an initial seed shouldn't be too bad, but you'll have to ingest terabytes of spammy/low quality content.

[Brybry]

wouldn't certificate transparency logs be a good way to collect most active domains?