[tialaramex]

The IETF probably isn't a useful example because it's a fairly strange thing. You probably couldn't (and shouldn't try to) do very much else that way. It's doubtful whether for example it constitutes an "organisation".

It has no formal legal existence whatsoever, so it can't own anything, including money, nor enter into any sort of contract with anybody, it doesn't have members, and the staff who make things happen aren't working for the IETF per se.

Something like ISRG (the organisation that provides the Let's Encrypt service you mentioned) is much more conventional, there's a not-for-profit legal entity in a specific place with employees, equipment and so on. It would be reasonable to run a TLD that way, and in fact I assume some of them are indeed run that way.

[geofft]

Who owns ietf.org etc.? I guess the answer is the Internet Society, which created the Public Interest Registry which currently owns .org (and which was the entity that intended to sell PIR to Ethos Capital), so maybe the IETF was a bad example for that reason too :)