[patrickmcmanus]

The IETF WG DBOUND tried to find a better solution to this problem and did not reach any consensus. fwiw.

https://datatracker.ietf.org/wg/dbound/about/

The current way most of this is handled is via a list published at publicsuffix.org (commonly known as the "Public Suffix List" or "PSL"), and the general goal is to accommodate anything people are using that for today. However, there are broadly speaking two use patterns. The first is a "top ancestor organization" case. In this case, the goal is to find a single superordinate name in the DNS tree that can properly make assertions about the policies and procedures of subordinate names. The second is to determine, given two different names, whether they are governed by the same administrative authority. The goal of the DBOUND working group is to develop a unified solution, if possible, for determining organizational domain boundaries. However, the working group may discover that the use cases require different solutions. Should that happen, the working group will develop those different solutions, using as many common pieces as it can.