> I spent 10 minutes searching for one in the article, in the RFC, in the wikipedia page, on google, to search for a .well-known example. Couldn't find one.

I don't know how that can be, since you claim to have found the RFC; the RFC straight-forwardly states,

> 5. IANA Considerations

> This specification updates the registration procedures for the "Well-Known URI" registry, first defined in [RFC5785]; see Section 3.1.

& then of course directs IANA to establish a registry. We'd expect this section, given the very nature of the RFC is that it establishes a collection of things, so that there is an IANA considerations section should be wholly unsurprising…

If you see the linked section…

> The "Well-Known URIs" registry is located at <https://www.iana.org/assignments/well-known-uris/>.

And there's a link to a listing of every standardized .well-known URI there is.

> What is it with technical documentations that go deep describing what it is in plenty words but refusing to give a single example?

The RFC provides an example in the form of "example", but also in the form of "robots.txt" (as a "it could have used this, had this existed", but what else could it have done?).

I've been setting up some federated servers (Matrix, activitypub) and I ran into .well_known/ paths in many of them. Webfinger resolver for activitypub and a more custom matrix server-to-server federation endpoint.