[AntiqueFig]

> I have seen websites which are on the tld with no sub domain.

Do you have any example of that?

[brewmarche]

http://ai./

It should only be possible on ccTLDs, this is not possible on newer gTLDs due to ICANN rules and I think no classic gTLD has it.

See: https://stackoverflow.com/a/40358071/4418149